Release v184 (#1106 )

Add Heroku-20 to deploy-runtimes default stacks list (#1104 )
Now `make deploy-runtimes` will build binaries for Heroku-20 by default too, without the need to pass it in via an explicit `STACKS=...`list. Closes @W-8233698@. [skip changelog]
2026-06-05 23:10:16 +00:00 · 2020-10-21 14:56:33 +01:00 · 2020-10-19 20:48:34 +01:00 · 2020-10-19 13:02:12 +01:00 · 2020-10-19 12:27:16 +01:00 · 2020-10-19 12:20:27 +01:00
90 changed files with 972 additions and 1920 deletions
@@ -0,0 +1,6 @@
+{
+  "productTag": "a1aB0000000MR0RIAW",
+  "issueTypeLabels": { "gus: story": "USER STORY", "gus: bug": "BUG P3" },
+  "defaultBuild": "Heroku Unscheduled",
+  "statusWhenClosed": "CLOSED"
+}
@@ -0,0 +1,15 @@
+version: 2
+updates:
+  - package-ecosystem: "pip"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    labels:
+      - "c: dependencies"
+
+  - package-ecosystem: "bundler"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    labels:
+      - "c: dependencies"
@@ -1,7 +0,0 @@
-repos:
-   repo: https://github.com/pre-commit/pre-commit-hooks
-    rev: v2.3.0
-    hooks:
-    -   id: check-yaml
-    -   id: end-of-file-fixer
-    -   id: trailing-whitespace
@@ -1,8 +1,8 @@
 language: minimal
-dist: bionic
+dist: focal
 branches:
  only:
-  - master
+  - main

 script:
  - make test STACK="${STACK}" TEST_CMD="${TEST_CMD}"
@@ -12,14 +12,13 @@ jobs:
  - name: Bash linting (shellcheck)
    script: make check
  - name: Hatchet integration tests
-    if: env(TRAVIS_PULL_REQUEST_SLUG) = env(TRAVIS_REPO_SLUG)
+    if: env(HEROKU_API_USER) IS present AND env(HEROKU_API_KEY) IS present
    language: ruby
    rvm:
-      - 2.6.6
+      - 2.7
    before_script:
-      - gem install bundler -v 1.16.2
-    script:
      - bundle exec hatchet ci:setup
+    script:
      - PARALLEL_SPLIT_TEST_PROCESSES=11 bundle exec parallel_split_test spec/hatchet/

 env:
@@ -35,10 +34,12 @@ env:
    - STACK=heroku-18 TEST_CMD=test/run-deps
    - STACK=heroku-18 TEST_CMD=test/run-versions
    - STACK=heroku-18 TEST_CMD=test/run-features
+
+    - STACK=heroku-20 TEST_CMD=test/run-deps
+    - STACK=heroku-20 TEST_CMD=test/run-versions
+    - STACK=heroku-20 TEST_CMD=test/run-features
  global:
    - HATCHET_RETRIES=3
    - IS_RUNNING_ON_CI=true
    - HATCHET_APP_LIMIT=80
    - HATCHET_DEPLOY_STRATEGY=git
-    - secure: yjtlPE5FbVxTKnjUy/tZUBgSEf4qADD3QOxtgziuid73S0U/1IEXlMGFULsQzIjtlHKmHeywZqpVVEpthIH4RuT7uoX1Pb7SSM/g0T8fT3VoEFbFK1uYl0oZQbUS4Klxv9tPiumj8if3m6ULEGIz1X0wZcMOC0tMLwVCnwmap0E=
-    - secure: ZeFTHWwnpIKE9nAqs88ocmiQh7bKce84lilGm5J23nf3N6V4wNyLwqlkvsM008WGBCaOg9AUx7ZunasT0ANsR5gLP3eV2UUg7ILdRgV2Gy13eNRFheC4PHdN92RqQ3aKoqlIv2K999xlhVjod0NzhkQQXB6PddfQINbuU7ks6As=
@@ -1,9 +1,63 @@
 # Python Buildpack Changelog

-# Master
+## Unreleased


-# 174 (2020-07-30)
+## v184 (2020-10-21)
+
+- Vendor buildpack-stdlib instead of fetching from S3 (#1100).
+- Fix metric names for metrics emitted within `sub_env` (#1099).
+
+## v183 (2020-10-12)
+
+- Add support for Heroku-20 (#968).
+
+## v182 (2020-10-06)
+
+- Python 3.9.0 is now available (CPython) (#1090).
+- Migrate from the `lang-python` S3 bucket to `heroku-buildpack-python` (#1089).
+- Remove `vendor/shunit2` (#1086).
+- Replace `BUILDPACK_VENDOR_URL` and `USE_STAGING_BINARIES` with `BUILDPACK_S3_BASE_URL` (#1085).
+
+## v181 (2020-09-29)
+
+- PyPy 2.7 and 3.6, version 7.3.2 are now available (Note: PyPy support is in beta) (#1081).
+
+## v180 (2020-09-24)
+
+- Python 3.8.6 is now available (CPython) (#1072).
+
+## v179 (2020-09-23)
+
+- Remove duplicate pipenv metric event (#1070).
+- Emit metrics for how the Python version was chosen for an app (#1069).
+- Emit Python version metric events for all builds, not just clean installs (#1066).
+
+## v178 (2020-09-07)
+
+- Python 3.5.10 is now available (CPython) (#1062).
+
+## v177 (2020-08-18)
+
+- Python 3.6.12 and 3.7.9 are now available (CPython) (#1054).
+- The default Python version for new apps is now 3.6.12 (previously 3.6.11) (#1054).
+
+## v176 (2020-08-12)
+
+- Rebuild the Python 3.4.10 archives with the correct version of Python (#1048).
+- Fix the security update version check message for apps using PyPy (#1040).
+- Remove `vendor/test-utils` (#1043).
+
+## v175 (2020-08-05)
+
+- Update pip from 20.0.2 to 20.1.1 for Python 2.7 and Python 3.5+ (#1030).
+- Update setuptools from 39.0.1 to: (#1024)
+  - 44.1.1 for Python 2.7
+  - 43.0.0 for Python 3.4
+  - 47.1.1 for Python 3.5+
+- Switch the `heroku-buildpack-python` repository default branch from `master` to `main` (#1029).
+
+## v174 (2020-07-30)

 - For repeat builds, also manage the installed versions of setuptools/wheel, rather than just that of pip (#1007).
 - Install an explicit version of wheel rather than the latest release at the time (#1007).
@@ -12,87 +66,85 @@
 - Install pip using itself rather than `get-pip.py` (#1007).
 - Disable pip's version check + cache when installing pip/setuptools/wheel (#1007).
 - Install setuptools from PyPI rather than a vendored copy (#1007).
- Reduce the number of environment variables exposed to `bin/{pre,post}_compile` and other subprocesses (#1011)
+- Reduce the number of environment variables exposed to `bin/{pre,post}_compile` and other subprocesses (#1011).

-# 173 (2020-07-21)
+## v173 (2020-07-21)

- Python 3.8.5 is now available (CPython)
+- Python 3.8.5 is now available (CPython).

-# 172 (2020-07-17)
+## v172 (2020-07-17)

- Python 3.8.4 is now available (CPython)
+- Python 3.8.4 is now available (CPython).

-# 171 (2020-07-07)
+## v171 (2020-07-07)

 - Python 3.6.11 and 3.7.8 are now available (CPython).

-# 170 (2020-05-19)
+## v170 (2020-05-19)

 - Python 2.7.18, 3.5.9, 3.7.7 and 3.8.3 are now available (CPython).
- PyPy 2.7 and 3.6, version 7.3.1 are now available (Note: PyPy support is in beta)
- Docs: Fix explanation of runtime.txt generation when using pipenv
- Bugfix: Correctly detect Python version when using a `python_version` of `3.8` in `Pipfile.lock`
+- PyPy 2.7 and 3.6, version 7.3.1 are now available (Note: PyPy support is in beta).
+- Docs: Fix explanation of runtime.txt generation when using pipenv.
+- Bugfix: Correctly detect Python version when using a `python_version` of `3.8` in `Pipfile.lock`.

--------------------------------------------------------------------------------
-
-# 169 (2020-04-22)
+## v169 (2020-04-22)

 - Add a Hatchet test for python 3.8.2
 - Set Code Owners to @heroku/langauges
 - Bugfix: Caching on subsequent redeploys
 - Update tests to support latest version of Python

-# 168 (2020-04-06)
+## v168 (2020-04-06)

 - Doc: Update Readme with version numbers
 - update Code Owners to include the Heroku Buildpack Maintainers team
- Deprecation warning: BUILD_WITH_GEO_LIBRARIES is now deprecated. See warning for details.
+- Deprecation warning: `BUILD_WITH_GEO_LIBRARIES` is now deprecated. See warning for details.
 - Clean up build log output
 - Update Python versions in README to match docs
 - Django version detection fixed, link updated

-# 167 (2020-03-26)
+## v167 (2020-03-26)

 - Add failcase for cache busting
 - Bugfix: Clearing pip dependencies

-# 166 (2020-03-05)
+## v166 (2020-03-05)

 - Correct ftp to https in vendored file
 - Warn for Django 1.11 approaching EOL, provide link to roadmap

-# 165 (2020-02-27)
+## v165 (2020-02-27)

 - Python 3.8.2 now available.

-# 164 (2020-02-20)
+## v164 (2020-02-20)

 - Update requirements.txt builds to use Pip 20.0.2
 - Download get-pip.py to tmpdir instead of root dir

-# 163 (2019-12-23)
+## v163 (2019-12-23)

 - New pythons released:
  Python 3.8.1, 3.7.6, 3.6.10 (CPython)
  Beta Release: Pypy 2.7 and 3.6, version 7.2.0

-# 162 (2019-12-06)
+## v162 (2019-12-06)

 - Bug fix: fragile sqlite3 install

-# 161 (2019-12-2)
+## v161 (2019-12-2)

 - Bug fix: Sqlite3 version bump

-# 160 (2019-10-23)
+## v160 (2019-10-23)

 - Bugfix: Pipenv no longer installs twice in CI

-# 159 (2019-10-22)
+## v159 (2019-10-22)

 - Python 2.7.17 now available on Heroku 18 and 16.

-# 158 (2019-10-21)
+## v158 (2019-10-21)

 - Python 3.7.5 and 3.8.0 now available on Heroku 18 and 16.
 - Add support for Python 3.8 branch
@@ -100,11 +152,11 @@
  - Test Improvements
 - Add support for staging binary testing

-# 157 (2019-09-18)
+## v157 (2019-09-18)

 - Typo fixes

-# 156 (2019-09-12)
+## v156 (2019-09-12)

 - Python 3.6.9 and 3.7.4 now available.

@@ -112,125 +164,125 @@
 - Build utility and documentation updates
 - Bump Hatchet tests to point at new default python version.

-# 155 (2019-08-22)
+## v155 (2019-08-22)

 add docs and make target for heroku-18 bob builds

-# 154 (2019-07-17)
+## v154 (2019-07-17)

 Fix python 3.5.7 formula actually building 3.7.2

-# 153 (2019-06-21)
+## v153 (2019-06-21)

 Hotfix for broken heroku-16 deploys

-# 152 (2019-04-04)
+## v152 (2019-04-04)

 Python 3.7.3 now available.

-# 151 (2019-03-21)
+## v151 (2019-03-21)

 Python 3.5.7 and 3.4.10 now available on all Heroku stacks.

-# 150 (2019-03-13)
+## v150 (2019-03-13)

 Python 2.7.16 now available on all Heroku stacks.

-# 149 (2019-03-04)
+## v149 (2019-03-04)

 Hotfix for broken Cedar 14 deploys

-# 148 (2019-02-21)
+## v148 (2019-02-21)

 No user facing changes, improving internal metrics

-# 147 (2019-02-07)
+## v147 (2019-02-07)

 Python 3.7.2 and 3.6.8 now available on all Heroku stacks.

-# 146 (2018-11-11)
+## v146 (2018-11-11)

 Python 3.7.1, 3.6.7, 3.5.6 and 3.4.9 now available on all Heroku stacks.

-# 145 (2018-11-08)
+## v145 (2018-11-08)

 Testing and tooling expanded to better support new runtimes

-# 144 (2018-10-10)
+## v144 (2018-10-10)

 Switch to cautious upgrade for Pipenv install to ensure the pinned pip version
 is used with Pipenv

-# 143 (2018-10-09)
+## v143 (2018-10-09)

-Add support for detecting SLUGIFY_USES_TEXT_UNIDECODE, which is required to
+Add support for detecting `SLUGIFY_USES_TEXT_UNIDECODE`, which is required to
 install Apache Airflow version 1.10 or higher.

-# 142 (2018-10-08)
+## v142 (2018-10-08)

 Improvements to Python install messaging

-# 139, 140, 141
+## v139, 140, 141

 No user-facing changes, documenting for version clarity

-# 138 (2018-08-01)
+## v138 (2018-08-01)

 Use stack image SQLite3 instead of vendoring

-# 137 (2018-07-17)
+## v137 (2018-07-17)

 Prevent 3.7.0 from appearing as unsupported in buildpack messaging.

-# 136 (2018-06-28)
+## v136 (2018-06-28)

 Upgrade to 3.6.6 and support 3.7.0 on all runtimes.

-# 135 (2018-05-29)
+## v135 (2018-05-29)

 Upgrade Pipenv to v2018.5.18.

-# 134 (2018-05-02)
+## v134 (2018-05-02)

 Default to 3.6.5, bugfixes.

-# 133
+## v133

 Fixes for Pip 10 release.

-# 132
+## v132

 Improve pip installation, with the release of v9.0.2.

-# 131
+## v131

 Fix bug with pip.

-# 130
+## v130

 Better upgrade strategy for pip.

-# 129
+## v129

 Don't upgrade pip (from v128).

-# 128
+## v128

 Upgrade pip, pin to Pipenv v11.8.2.

-# 127
+## v127

 Pin to Pipenv v11.7.1.

-# 126
+## v126

 Bugfixes.

-# 125
+## v125

 Bugfixes.

-# 124
+## v124

 Update buildpack to automatically install `[dev-packages]` during Heroku CI Pipenv builds.

@@ -239,101 +291,101 @@ Update buildpack to automatically install `[dev-packages]` during Heroku CI Pipe
 - No longer warn if there is no `Procfile`.
 - Update Pipenv's "3.6" runtime specifier to point to "3.6.4".

-# 123
+## v123

 Update gunicorn `init.d` script to allow overrides.

-# 122
+## v122

 Update default Python to v3.6.4.

-# 121
+## v121

 Update default Python to v3.6.3.

-# 120
+## v120

 Use `$ pipenv --deploy`.

-# 119
+## v119

 Improvements to Pipenv support, warning on unsupported Python versions.

 - We now warn when a user is not using latest 2.x or 3.x Python.
 - Heroku now supports `[requires]` `python_full_version` in addition to `python_version`.

-# 118
+## v118

 Improvements to Pipenv support.

-# 117
+## v117

 Bug fix.

-# 116
+## v116

 Vendoring improvements.

 - Geos libraries should work on Heroku-16 now.
 - The libffi/libmemcached vendoring step is now skipped on Heroku-16 (since they are installed in the base image).

-# 115
+## v115

 Revert a pull request.

 - No longer using `sub_env` for `pip install` step.

-# 114
+## v114

 - Bugfixes.

 Blacklisting `PYTHONHOME` and `PYTHONPATH` for older apps. Upgrades to nltk support.

-# 113
+## v113

 Updates to Pipenv support.

-# 112
+## v112

 Bugfix.

 - Fixed grep output bug.

-# 111
+## v111

 Linting, bugfixes.

-# 110
+## v110

 Update default Python to 3.6.2.

-# 109
+## v109

 Update Default Python to 3.6.1, bugfixes.

 - Fixed automatic pip uninstall of dependencies removed from requirements.txt.

-# 108
+## v108

 Fix output for collectstatic step.

-# 107
+## v107

 Bugfix for C dependency installation.

-# 106
+## v106

- Don't install packages that could mess up packaging.
+Don't install packages that could mess up packaging.

 - The Python buildpack will automatically remove `six`, `pyparsing`, `appdirs`,
   `setuptools`, and `distribute` from a `requirements.txt` file now, as these
   packages are provided by the Python buildpack.

- # 105
+## v105

- Improvements to output messaging.
+Improvements to output messaging.

-# 104
+## v104

 General improvements.

@@ -343,52 +395,52 @@ General improvements.

 [395]: https://github.com/heroku/heroku-buildpack-python/pull/395

-## 103
+## v103

 Bug fixes and improvements.

 - Fix for Pipenv.
 - Fix for Heroku CI.
- Improve handling of WEB_CONCURRENCY when using multiple buildpacks.
- Adjust environment variables set during the build to more closely match those in the dyno environment (DYNO is now available, STACK is not).
+- Improve handling of `WEB_CONCURRENCY` when using multiple buildpacks.
+- Adjust environment variables set during the build to more closely match those in the dyno environment (`DYNO` is now available, `STACK` is not).
 - Restore the build cache prior to running bin/pre_compile.

-## 102
+## v102

 Buildpack code cleanup.

 - Improved messaging around NLTK.

-## 101
+## v101

 Updated setuptools installation method.

 - Improved pipenv support.

-## 100
+## v100

 Preliminary pipenv support.

-## 99
+## v99

 Cleanup.

-## 98
+## v98

 Official NLTK support and other improvements.

 - Support for `nltk.txt` file for declaring corpora to be downloaded.
- Leading zeros for auto-set WEB_CONCURRENCY.
+- Leading zeros for auto-set `WEB_CONCURRENCY`.

-## 97
+## v97

 Improved egg-link functionality.

-## 96
+## v96

 Bugfix.

-## 95
+## v95

 Improved output support.

@@ -424,7 +476,7 @@ Fixed bug with editable pip installations.

 Updated default Python 2.7.13.

- Python 2.7.13 uses UCS-4 build, more compatibile with linux wheels.
+- Python 2.7.13 uses UCS-4 build, more compatible with linux wheels.
 - Updated setuptools to v32.1.0.

 ## v86
@@ -450,7 +502,7 @@ Support for Heroku CI.

 ## v82 (2016-08-22)

-Update to library detection mechnisms (pip-pop).
+Update to library detection mechanisms (pip-pop).

 - Updated setuptools to v25.5.0

@@ -524,7 +576,7 @@ Revert to v66.

 ## v68 (2015-10-12)

-Fixed .heroku/venv error with modern apps.
+Fixed `.heroku/venv` error with modern apps.

 ## v67 (2015-10-12)

@@ -549,7 +601,6 @@ Updated Pip and Setuptools.
 - Setuptools updated to v18.3.2
 - Pip updated to v7.1.2

-
 ## v62 (2015-08-07)

 Updated Pip and Setuptools.
@@ -1,68 +1,50 @@
 GEM
  remote: https://rubygems.org/
  specs:
-    activesupport (6.0.3.1)
-      concurrent-ruby (~> 1.0, >= 1.0.2)
-      i18n (>= 0.7, < 2)
-      minitest (~> 5.1)
-      tzinfo (~> 1.1)
-      zeitwerk (~> 2.2, >= 2.2.2)
-    concurrent-ruby (1.1.6)
-    diff-lcs (1.3)
+    diff-lcs (1.4.4)
    erubis (2.7.0)
-    excon (0.73.0)
-    heroics (0.0.25)
+    excon (0.78.0)
+    heroics (0.1.1)
      erubis (~> 2.0)
      excon
      moneta
      multi_json (>= 1.9.2)
-    heroku_hatchet (5.0.3)
+    heroku_hatchet (7.3.3)
      excon (~> 0)
-      minitest-retry (~> 0.1.9)
-      platform-api (~> 2)
-      repl_runner (~> 0.0.3)
+      platform-api (~> 3)
      rrrretry (~> 1)
-      thor (~> 0)
+      thor (~> 1)
      threaded (~> 0)
-    i18n (1.8.2)
-      concurrent-ruby (~> 1.0)
-    minitest (5.14.1)
-    minitest-retry (0.1.9)
-      minitest (>= 5.0)
    moneta (1.0.0)
-    multi_json (1.14.1)
-    parallel (1.19.1)
-    parallel_split_test (0.7.0)
+    multi_json (1.15.0)
+    parallel (1.19.2)
+    parallel_split_test (0.8.0)
      parallel (>= 0.5.13)
      rspec (>= 3.1.0)
-    platform-api (2.2.0)
-      heroics (~> 0.0.25)
+    platform-api (3.0.0)
+      heroics (~> 0.1.1)
      moneta (~> 1.0.0)
-    rake (12.3.3)
-    repl_runner (0.0.3)
-      activesupport
+      rate_throttle_client (~> 0.1.0)
+    rake (13.0.1)
+    rate_throttle_client (0.1.2)
    rrrretry (1.0.0)
-    rspec (3.8.0)
-      rspec-core (~> 3.8.0)
-      rspec-expectations (~> 3.8.0)
-      rspec-mocks (~> 3.8.0)
-    rspec-core (3.8.0)
-      rspec-support (~> 3.8.0)
-    rspec-expectations (3.8.1)
+    rspec (3.9.0)
+      rspec-core (~> 3.9.0)
+      rspec-expectations (~> 3.9.0)
+      rspec-mocks (~> 3.9.0)
+    rspec-core (3.9.2)
+      rspec-support (~> 3.9.3)
+    rspec-expectations (3.9.2)
      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-mocks (3.8.0)
+      rspec-support (~> 3.9.0)
+    rspec-mocks (3.9.1)
      diff-lcs (>= 1.2.0, < 2.0)
-      rspec-support (~> 3.8.0)
-    rspec-retry (0.6.1)
+      rspec-support (~> 3.9.0)
+    rspec-retry (0.6.2)
      rspec-core (> 3.3)
-    rspec-support (3.8.0)
-    thor (0.20.3)
-    thread_safe (0.3.6)
+    rspec-support (3.9.3)
+    thor (1.0.1)
    threaded (0.0.4)
-    tzinfo (1.2.7)
-      thread_safe (~> 0.1)
-    zeitwerk (2.3.0)

 PLATFORMS
  ruby
@@ -1,15 +1,18 @@
 # These targets are not files
-.PHONY: check test buildenv-heroku-16 buildenv-heroku-18 tools
+.PHONY: check test builder-image buildenv deploy-runtimes tools

 STACK ?= heroku-18
+STACKS ?= cedar-14 heroku-16 heroku-18 heroku-20
 TEST_CMD ?= test/run-versions && test/run-features && test/run-deps
+ENV_FILE ?= builds/dockerenv.default
+BUILDER_IMAGE_PREFIX := heroku-python-build

 ifeq ($(STACK),cedar-14)
 	# Cedar-14 doesn't have a build image varient.
-	IMAGE_TAG := heroku/cedar:14
+	STACK_IMAGE_TAG := heroku/cedar:14
 else
 	# Converts a stack name of `heroku-NN` to its build Docker image tag of `heroku/heroku:NN-build`.
-	IMAGE_TAG := heroku/$(subst -,:,$(STACK))-build
+	STACK_IMAGE_TAG := heroku/$(subst -,:,$(STACK))-build
 endif

 check:
@@ -19,37 +22,42 @@ check:

 test:
 	@echo "Running tests using: STACK=$(STACK) TEST_CMD='$(TEST_CMD)'"
-	@echo ""
-	@docker run --rm -it -v $(PWD):/buildpack:ro -e "STACK=$(STACK)" "$(IMAGE_TAG)" bash -c 'cp -r /buildpack /buildpack_test && cd /buildpack_test && $(TEST_CMD)'
-	@echo ""
-
-buildenv-heroku-16:
-	@echo "Creating build environment (heroku-16)..."
 	@echo
-	@docker build --pull -f $(shell pwd)/builds/heroku-16.Dockerfile -t python-buildenv-heroku-16 .
+	@docker run --rm -it -v $(PWD):/buildpack:ro -e "STACK=$(STACK)" "$(STACK_IMAGE_TAG)" bash -c 'cp -r /buildpack /buildpack_test && cd /buildpack_test && $(TEST_CMD)'
+	@echo
+
+builder-image:
+	@echo "Generating binary builder image for $(STACK)..."
+	@echo
+	@docker build --pull -f builds/$(STACK).Dockerfile -t "$(BUILDER_IMAGE_PREFIX)-$(STACK)" .
+	@echo
+
+buildenv: builder-image
+	@echo "Starting build environment for $(STACK)..."
 	@echo
 	@echo "Usage..."
 	@echo
-	@echo "  $$ export AWS_ACCESS_KEY_ID=foo AWS_SECRET_ACCESS_KEY=bar  # Optional unless deploying"
-	@echo "  $$ bob build runtimes/python-2.7.13"
-	@echo "  $$ bob deploy runtimes/python-2.7.13"
+	@echo "  $$ bob build runtimes/python-X.Y.Z"
 	@echo
-	@docker run -it --rm python-buildenv-heroku-16
+	@docker run --rm -it --env-file="$(ENV_FILE)" -v $(PWD)/builds:/app/builds "$(BUILDER_IMAGE_PREFIX)-$(STACK)" bash

-buildenv-heroku-18:
-	@echo "Creating build environment (heroku-18)..."
+deploy-runtimes:
+ifndef RUNTIMES
+	$(error No runtimes specified! Use: "make deploy-runtimes RUNTIMES='python-X.Y.Z ...' [STACKS='heroku-18 ...'] [ENV_FILE=...]")
+endif
+	@echo "Using: RUNTIMES='$(RUNTIMES)' STACKS='$(STACKS)' ENV_FILE='$(ENV_FILE)'"
 	@echo
-	@docker build --pull -f $(shell pwd)/builds/heroku-18.Dockerfile -t python-buildenv-heroku-18 .
-	@echo
-	@echo "Usage..."
-	@echo
-	@echo "  $$ export AWS_ACCESS_KEY_ID=foo AWS_SECRET_ACCESS_KEY=bar  # Optional unless deploying"
-	@echo "  $$ bob build runtimes/python-2.7.13"
-	@echo "  $$ bob deploy runtimes/python-2.7.13"
-	@echo
-	@docker run -it --rm python-buildenv-heroku-18
+	@set -eu; for stack in $(STACKS); do \
+		$(MAKE) builder-image STACK=$${stack}; \
+		for runtime in $(RUNTIMES); do \
+			echo "Generating/deploying $${runtime} for $${stack}..."; \
+			echo; \
+			docker run --rm -it --env-file="$(ENV_FILE)" "$(BUILDER_IMAGE_PREFIX)-$${stack}" bob deploy "runtimes/$${runtime}"; \
+			echo; \
+		done; \
+	done

 tools:
 	git clone https://github.com/kennethreitz/pip-pop.git
 	mv pip-pop/bin/* vendor/pip-pop/
-	rm -fr pip-pop
+	rm -rf pip-pop
@@ -2,7 +2,7 @@

 # Heroku Buildpack: Python

-[![Build Status](https://travis-ci.org/heroku/heroku-buildpack-python.svg?branch=master)](https://travis-ci.org/heroku/heroku-buildpack-python)
+[![Build Status](https://travis-ci.com/heroku/heroku-buildpack-python.svg?branch=main)](https://travis-ci.com/heroku/heroku-buildpack-python)

 This is the official [Heroku buildpack](https://devcenter.heroku.com/articles/buildpacks) for Python apps.

@@ -16,7 +16,7 @@ See it in Action
 $ ls
 my-application		requirements.txt	runtime.txt

-$ git push heroku master
+$ git push heroku main
 Counting objects: 4, done.
 Delta compression using up to 8 threads.
 Compressing objects: 100% (2/2), done.
@@ -26,7 +26,7 @@ remote: Compressing source files... done.
 remote: Building source:
 remote:
 remote: -----> Python app detected
-remote: -----> Installing python-3.7.4
+remote: -----> Installing python
 remote: -----> Installing pip
 remote: -----> Installing SQLite3
 remote: -----> Installing requirements with pip
@@ -44,7 +44,7 @@ A `requirements.txt` must be present at the root of your application's repositor

 To specify your python version, you also need a `runtime.txt` file - unless you are using the default Python runtime version.

-Current default Python Runtime: Python 3.6.9
+Current default Python Runtime: Python 3.6.12

 Alternatively, you can provide a `setup.py` file, or a `Pipfile`.
 Using `pipenv` will generate `runtime.txt` at build time if one of the field `python_version` or `python_full_version` is specified in the `requires` section of your `Pipfile`.
@@ -62,9 +62,10 @@ Specify a Python Runtime

 Supported runtime options include:

- `python-3.8.5`
- `python-3.7.8`
- `python-3.6.11`
+- `python-3.9.0`
+- `python-3.8.6`
+- `python-3.7.9`
+- `python-3.6.12`
 - `python-2.7.18`

 ## Tests
@@ -15,10 +15,8 @@
 # Fail fast and fail hard.
 set -eo pipefail

-# Boostrap the Buildpack Standard Library.
-# Disable unused env var warning since shellcheck doesn't know about the stdlib.
-# shellcheck disable=2034
-BPLOG_PREFIX="buildpack.python"
+# Used by buildpack-stdlib's metrics features.
+export BPLOG_PREFIX="buildpack.python"
 export BUILDPACK_LOG_FILE=${BUILDPACK_LOG_FILE:-/dev/null}

 [ "$BUILDPACK_XTRACE" ] && set -o xtrace
@@ -37,23 +35,27 @@ ENV_DIR=$3
 # Export Path variables, for use in sub-scripts.
 export BUILD_DIR CACHE_DIR ENV_DIR

-# Set the Buildpack's internet target for downloading Python distributions.
-# The user can provide BUILDPACK_VENDOR_URL to specify a custom target.
+# Set the base URL for downloading buildpack assets like Python runtimes.
+# The user can provide BUILDPACK_S3_BASE_URL to specify a custom target.
 # Note: this is designed for non-Heroku use, as it does not use the user-provided
 # environment variable mechanism (the ENV_DIR).
-VENDOR_URL="https://lang-python.s3.amazonaws.com/$STACK"
-if [[ -n ${BUILDPACK_VENDOR_URL:-} ]]; then
-    VENDOR_URL="$BUILDPACK_VENDOR_URL"
-elif [[ -n ${USE_STAGING_BINARIES} ]]; then
-    VENDOR_URL="$USE_STAGING_BINARIES/$STACK"
+if [[ "${STACK}" == "cedar-14" ]]; then
+  # Since Cedar-14 is EOL on 2020-11-02 it's not worth migrating it to the new bucket.
+  DEFAULT_S3_BASE_URL='https://lang-python.s3.amazonaws.com'
+else
+  DEFAULT_S3_BASE_URL='https://heroku-buildpack-python.s3.amazonaws.com'
 fi
-export VENDOR_URL
+S3_BASE_URL="${BUILDPACK_S3_BASE_URL:-${DEFAULT_S3_BASE_URL}}"
+# This has to be exported since it's used by the geo-libs step which is run in a subshell.
+# TODO: Stop exporting once the geo-libs step is removed or no longer uses `sub_env`.
+export S3_BASE_URL

 # Default Python Versions
 # shellcheck source=bin/default_pythons
 source "$BIN_DIR/default_pythons"

 # Supported Python Branches
+PY39="python-3.9"
 PY38="python-3.8"
 PY37="python-3.7"
 PY36="python-3.6"
@@ -137,6 +139,10 @@ export LIBRARY_PATH=/app/.heroku/vendor/lib:/app/.heroku/python/lib:$LIBRARY_PAT
 export LD_LIBRARY_PATH=/app/.heroku/vendor/lib:/app/.heroku/python/lib:$LD_LIBRARY_PATH
 export PKG_CONFIG_PATH=/app/.heroku/vendor/lib/pkg-config:/app/.heroku/python/lib/pkg-config:$PKG_CONFIG_PATH

+# Global pip options (https://pip.pypa.io/en/stable/user_guide/#environment-variables).
+# Disable pip's warnings about EOL Python since we show our own.
+export PIP_NO_PYTHON_VERSION_WARNING=1
+
 # The Application Code
 # --------------------

@@ -185,7 +191,7 @@ source "$BIN_DIR/steps/hooks/pre_compile"
 # continue to use that version of Python in perpituity (warnings will be raised if
 # they are out–of–date).
 if [ -f "$CACHE_DIR/.heroku/python-version" ]; then
-  DEFAULT_PYTHON_VERSION=$(cat "$CACHE_DIR/.heroku/python-version")
+  CACHED_PYTHON_VERSION=$(cat "$CACHE_DIR/.heroku/python-version")
 fi

 # We didn't always record the stack version. This code is in place because of that.
@@ -202,9 +208,14 @@ fi
 # shellcheck source=bin/steps/pipenv-python-version
 source "$BIN_DIR/steps/pipenv-python-version"

-# If no runtime was provided by the user, assume the default Python runtime version.
-if [ ! -f runtime.txt ]; then
-  echo "$DEFAULT_PYTHON_VERSION" > runtime.txt
+if [[ -f runtime.txt ]]; then
+  mcount "version.reason.python.specified"
+elif [[ -n "${CACHED_PYTHON_VERSION:-}" ]]; then
+  mcount "version.reason.python.cached"
+  echo "${CACHED_PYTHON_VERSION}" > runtime.txt
+else
+  mcount "version.reason.python.default"
+  echo "${DEFAULT_PYTHON_VERSION}" > runtime.txt
 fi

 # Create the directory for .profile.d, if it doesn't exist.
@@ -300,7 +311,7 @@ mtime "nltk.download.time" "${start}"
 # and copying it into the proper place (the logical place to do this was early, but it must be done here).
 # In CI, $BUILD_DIR is /app.
 if [[ ! "$BUILD_DIR" == "/app" ]]; then
-  rm -fr "$BUILD_DIR/.heroku/src"
+  rm -rf "$BUILD_DIR/.heroku/src"
  deep-cp /app/.heroku/src "$BUILD_DIR/.heroku/src"
 fi

@@ -5,12 +5,13 @@
 # the env vars to subprocesses.
 # shellcheck disable=2034

-DEFAULT_PYTHON_VERSION="python-3.6.11"
-LATEST_38="python-3.8.5"
-LATEST_37="python-3.7.8"
-LATEST_36="python-3.6.11"
-LATEST_35="python-3.5.9"
+DEFAULT_PYTHON_VERSION="python-3.6.12"
+LATEST_39="python-3.9.0"
+LATEST_38="python-3.8.6"
+LATEST_37="python-3.7.9"
+LATEST_36="python-3.6.12"
+LATEST_35="python-3.5.10"
 LATEST_34="python-3.4.10"
 LATEST_27="python-2.7.18"
-PYPY_36="pypy3.6-7.3.1"
-PYPY_27="pypy2.7-7.3.1"
+LATEST_PYPY_36="pypy3.6-7.3.2"
+LATEST_PYPY_27="pypy2.7-7.3.2"
@@ -10,7 +10,7 @@
 # This script is invoked by [`bin/compile`](/).

 # The location of the pre-compiled cryptography binary.
-VENDORED_GDAL="${VENDOR_URL}/libraries/vendor/gdal.tar.gz"
+VENDORED_GDAL="${S3_BASE_URL}/${STACK}/libraries/vendor/gdal.tar.gz"

 PKG_CONFIG_PATH="/app/.heroku/vendor/lib/pkgconfig:$PKG_CONFIG_PATH"

@@ -21,8 +21,11 @@ source "$BIN_DIR/utils"
 # If GDAL exists within requirements, use vendored gdal.
 if (pip-grep -s requirements.txt GDAL gdal pygdal &> /dev/null) then

-  if [ ! -f ".heroku/vendor/bin/gdalserver" ]; then
+  if [[ ! -f ".heroku/vendor/bin/gdalserver" && "${STACK}" == 'heroku-20' ]]; then
+    puts-warn "The buildpack's built-in GDAL functonality is not supported on Heroku-20."
+    puts-warn "Please use this buildpack instead: https://github.com/heroku/heroku-geo-buildpack"

+  elif [[ ! -f ".heroku/vendor/bin/gdalserver" ]]; then
    puts-warn "The vendored GDAL package in the Heroku Python Buildpack now deprecated."
    puts-warn "To enable GDAL use an alternative buildpack is available here - https://github.com/heroku/heroku-geo-buildpack"

@@ -10,9 +10,9 @@
 # This script is invoked by [`bin/compile`](/).

 # The location of the pre-compiled cryptography binary.
-VENDORED_GDAL="${VENDOR_URL}/libraries/vendor/gdal.tar.gz"
-VENDORED_GEOS="${VENDOR_URL}/libraries/vendor/geos.tar.gz"
-VENDORED_PROJ="${VENDOR_URL}/libraries/vendor/proj.tar.gz"
+VENDORED_GDAL="${S3_BASE_URL}/${STACK}/libraries/vendor/gdal.tar.gz"
+VENDORED_GEOS="${S3_BASE_URL}/${STACK}/libraries/vendor/geos.tar.gz"
+VENDORED_PROJ="${S3_BASE_URL}/${STACK}/libraries/vendor/proj.tar.gz"

 PKG_CONFIG_PATH="/app/.heroku/vendor/lib/pkgconfig:$PKG_CONFIG_PATH"

@@ -20,8 +20,11 @@ PKG_CONFIG_PATH="/app/.heroku/vendor/lib/pkgconfig:$PKG_CONFIG_PATH"
 # shellcheck source=bin/utils
 source "$BIN_DIR/utils"

-# If GDAL exists within requirements, use vendored gdal.
-if [[ "$BUILD_WITH_GEO_LIBRARIES" ]]; then
+if [[ "$BUILD_WITH_GEO_LIBRARIES" && "${STACK}" == 'heroku-20' ]]; then
+  puts-warn "The GDAL, GEOS and PROJ binaries and BUILD_WITH_GEO_LIBRARIES functonality is not supported on Heroku-20."
+  puts-warn "Please use this buildpack for GDAL, GEOS and PROJ: https://github.com/heroku/heroku-geo-buildpack"
+  puts-warn "To hide this message, unset the BUILD_WITH_GEO_LIBRARIES variable using: heroku config:unset BUILD_WITH_GEO_LIBRARIES"
+elif [[ "$BUILD_WITH_GEO_LIBRARIES" ]]; then
  mcount "buildvar.BUILD_WITH_GEO_LIBRARIES"

  puts-warn "The GDAL, GEOS and PROJ binaries and BUILD_WITH_GEO_LIBRARIES functonality are now deprecated."
@@ -16,7 +16,7 @@ if [ ! "$SKIP_PIP_INSTALL" ]; then
      mcount "failure.bad-requirements"
    fi

-    rm -fr requirements-declared.txt
+    rm -rf requirements-declared.txt

    if [[ -s .heroku/python/requirements-stale.txt ]]; then
      puts-step "Uninstalling stale dependencies"
@@ -9,10 +9,7 @@ set -e
 if [[ -f Pipfile.lock ]]; then
    if [[ -f .heroku/python/Pipfile.lock.sha256 ]]; then
        if [[ $(openssl dgst -sha256 Pipfile.lock) == $(cat .heroku/python/Pipfile.lock.sha256) ]]; then
-            # Measure that we're using Pipenv.
-            mcount "tool.pipenv"
-
-            # Don't skip installation of there are git deps.
+            # Don't skip installation if there are git deps.
            if ! grep -q 'git' Pipfile.lock; then
                echo "Skipping installation, as Pipfile.lock hasn't changed since last deploy." | indent

@@ -30,6 +30,9 @@ if [[ -f $BUILD_DIR/Pipfile ]]; then
                if [ "$PYTHON" = 3.8 ]; then
                    echo "$LATEST_38" > "$BUILD_DIR/runtime.txt"
                fi
+                if [ "$PYTHON" = 3.9 ]; then
+                    echo "$LATEST_39" > "$BUILD_DIR/runtime.txt"
+                fi
            fi


@@ -15,7 +15,7 @@ if [[ "$STACK" != "cedar-14" ]]; then
 fi

 # The location of the pre-compiled libmemcached binary.
-VENDORED_MEMCACHED="${VENDOR_URL}/libraries/vendor/libmemcache.tar.gz"
+VENDORED_MEMCACHED="${S3_BASE_URL}/${STACK}/libraries/vendor/libmemcache.tar.gz"

 # Syntax sugar.
 # shellcheck source=bin/utils
@@ -5,9 +5,10 @@ runtime-fixer runtime.txt
 PYTHON_VERSION=$(cat runtime.txt)

 # The location of the pre-compiled python binary.
-VENDORED_PYTHON="${VENDOR_URL}/runtimes/$PYTHON_VERSION.tar.gz"
+VENDORED_PYTHON="${S3_BASE_URL}/${STACK}/runtimes/${PYTHON_VERSION}.tar.gz"

 SECURITY_UPDATE="Python has released a security update! Please consider upgrading to"
+SECURITY_UPDATE_PYPY="The PyPy project has released a security update! Please consider upgrading to"

 ONLY_SUPPORTED_2_VERSION="Only the latest version of Python 2 is supported on the platform. Please consider upgrading to"

@@ -15,6 +16,12 @@ PYTHON_2_EOL_UPDATE="Python 2 has reached it's community EOL. Upgrade your Pytho

 # check if runtime exists
 if curl --output /dev/null --silent --head --fail "$VENDORED_PYTHON"; then
+  if [[ "$PYTHON_VERSION" == $PY39* ]]; then
+    if [ "$PYTHON_VERSION" != "$LATEST_39" ]; then
+      puts-warn "$SECURITY_UPDATE" "$LATEST_39"
+      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
+    fi
+  fi
  if [[ "$PYTHON_VERSION" == $PY38* ]]; then
    # do things to alert the user of security release available
    if [ "$PYTHON_VERSION" != "$LATEST_38" ]; then
@@ -51,11 +58,9 @@ if curl --output /dev/null --silent --head --fail "$VENDORED_PYTHON"; then
    fi
  fi
  if [[ "$PYTHON_VERSION" == $PY27* ]]; then
+    puts-warn "$PYTHON_2_EOL_UPDATE"
+    echo "       Learn More: https://devcenter.heroku.com/articles/python-2-7-eol-faq"
    # security update note
-    if [[ "$(date "+%Y")" -gt "2019" ]]; then
-      puts-warn "$PYTHON_2_EOL_UPDATE"
-      echo "       Learn More: https://devcenter.heroku.com/articles/python-2-7-eol-faq"
-    fi
    if [ "$PYTHON_VERSION" != "$LATEST_27" ]; then
      puts-warn "$ONLY_SUPPORTED_2_VERSION" "$LATEST_27"
      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
@@ -63,15 +68,15 @@ if curl --output /dev/null --silent --head --fail "$VENDORED_PYTHON"; then
  fi
  if [[ "$PYTHON_VERSION" == $PYPY27* ]]; then
    # security update note
-    if [ "$PYTHON_VERSION" != "$PYPY_27" ]; then
-      puts-warn "Could not find that Pypy version. Did you mean" "${PYPY_27}?"
+    if [ "$PYTHON_VERSION" != "$LATEST_PYPY_27" ]; then
+      puts-warn "$SECURITY_UPDATE_PYPY" "$LATEST_PYPY_27"
      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
    fi
  fi
  if [[ "$PYTHON_VERSION" == $PYPY36* ]]; then
    # security update note
-    if [ "$PYTHON_VERSION" != "$PYPY_36" ]; then
-      puts-warn "Could not find that Pypy version. Did you mean" "${PYPY_36}?"
+    if [ "$PYTHON_VERSION" != "$LATEST_PYPY_36" ]; then
+      puts-warn "$SECURITY_UPDATE_PYPY" "$LATEST_PYPY_36"
      echo "       Learn More: https://devcenter.heroku.com/articles/python-runtimes"
    fi
  fi
@@ -81,15 +86,17 @@ else
  exit 1
 fi

+mcount "version.python.${PYTHON_VERSION}"
+
 if [[ "$STACK" != "$CACHED_PYTHON_STACK" ]]; then
    puts-step "Stack has changed from $CACHED_PYTHON_STACK to $STACK, clearing cache"
-    rm -fr .heroku/python-stack .heroku/python-version .heroku/python .heroku/vendor .heroku/python .heroku/python-sqlite3-version
+    rm -rf .heroku/python-stack .heroku/python-version .heroku/python .heroku/vendor .heroku/python .heroku/python-sqlite3-version
 fi

 if [ -f .heroku/python-version ]; then
  if [ ! "$(cat .heroku/python-version)" = "$PYTHON_VERSION" ]; then
      puts-step "Found $(cat .heroku/python-version), removing"
-      rm -fr .heroku/python
+      rm -rf .heroku/python
  else
    SKIP_INSTALL=1
  fi
@@ -120,8 +127,6 @@ if [ ! "$SKIP_INSTALL" ]; then
    # Prepare destination directory.
    mkdir -p .heroku/python

-    mcount "version.python.$PYTHON_VERSION"
-
    if ! curl "${VENDORED_PYTHON}" -s | tar zxv -C .heroku/python &> /dev/null; then
      puts-warn "Requested runtime ($PYTHON_VERSION) is not available for this stack ($STACK)."
      puts-warn "Aborting.  More info: https://devcenter.heroku.com/articles/python-support"
@@ -137,14 +142,20 @@ fi

 set -e

-PIP_VERSION='20.0.2'
-SETUPTOOLS_VERSION='39.0.1'
+PIP_VERSION='20.1.1'
+# Must use setuptools <47.2.0 until we fix:
+# https://github.com/heroku/heroku-buildpack-python/issues/1006
+SETUPTOOLS_VERSION='47.1.1'
 WHEEL_VERSION='0.34.2'

 if [[ "${PYTHON_VERSION}" == ${PY34}* ]]; then
-  # Python 3.4 support was dropped in pip 19.2+ and wheel 0.34.0+.
+  # Python 3.4 support was dropped in pip 19.2+, setuptools 44+ and wheel 0.34+.
  PIP_VERSION='19.1.1'
+  SETUPTOOLS_VERSION='43.0.0'
  WHEEL_VERSION='0.33.6'
+elif [[ "${PYTHON_VERSION}" == ${PY27}* || "${PYTHON_VERSION}" == ${PYPY27}* ]]; then
+  # Python 2.7 support was dropped in setuptools 45+.
+  SETUPTOOLS_VERSION='44.1.1'
 fi

 # We don't use get-pip.py, since:
@@ -155,7 +166,7 @@ fi
 # Instead, we use the pip wheel to install itself, using the method described here:
 # https://github.com/pypa/pip/issues/2351#issuecomment-69994524
 PIP_WHEEL_FILENAME="pip-${PIP_VERSION}-py2.py3-none-any.whl"
-PIP_WHEEL_URL="https://lang-python.s3.amazonaws.com/common/${PIP_WHEEL_FILENAME}"
+PIP_WHEEL_URL="${S3_BASE_URL}/common/${PIP_WHEEL_FILENAME}"
 PIP_WHEEL="${TMPDIR:-/tmp}/${PIP_WHEEL_FILENAME}"

 if ! curl -sSf "${PIP_WHEEL_URL}" -o "$PIP_WHEEL"; then
@@ -2,12 +2,13 @@
 shopt -s extglob
 shopt -s nullglob

-# The standard library.
-if [[ ! -f  /tmp/stdlib.sh ]]; then
-  curl --retry 3 -s https://lang-common.s3.amazonaws.com/buildpack-stdlib/v8/stdlib.sh > /tmp/stdlib.sh
-fi
-# shellcheck source=/dev/null
-source /tmp/stdlib.sh
+# This is necessary since this script is sometimes sourced from
+# subshells that don't have the variables from bin/compile.
+# Remove this once we no longer wrap all the things in `sub_env`.
+BIN_DIR=$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)
+ROOT_DIR=$(dirname "${BIN_DIR}")
+# shellcheck source=vendor/buildpack-stdlib_v8.sh
+source "${ROOT_DIR}/vendor/buildpack-stdlib_v8.sh"

 if [ "$(uname)" == Darwin ]; then
    sed() { command sed -l "$@"; }
@@ -1,57 +1,80 @@
 # Python Buildpack Binaries

-## Building the Docker Images
-
-**After every change to your formulae, perform the following** from the root of the Git repository (not from `builds/`) to rebuild the images for each stack:
-
-    $ docker build --pull --tag heroku-python-build-cedar-14 --file $(pwd)/builds/cedar-14.Dockerfile .
-    $ docker build --pull --tag heroku-python-build-heroku-16 --file $(pwd)/builds/heroku-16.Dockerfile .
-    $ docker build --pull --tag heroku-python-build-heroku-18 --file $(pwd)/builds/heroku-18.Dockerfile .
-
-## Using the Image
-
-You can e.g. `bash` into each of the images you built using their tag:
-
-    docker run --rm -ti heroku-python-build-cedar-14 bash
-    docker run --rm -ti heroku-python-build-heroku-16 bash
-    docker run --rm -ti heroku-python-build-heroku-18 bash
-
-You then have a shell where you can run `bob build`, `bob deploy`, and so forth. You can of course also invoke these programs directly with `docker run`:
-
-    docker run --rm -ti heroku-python-build-heroku-18 bob build runtimes/python-2.7.15
-
-In order to `bob deploy`, AWS credentials must be set up, as well as name and prefix of your custom S3 bucket (unless you're deploying to the Heroku production buckets that are pre-defined in each `Dockerfile`); see next section for details.
+The binaries for this buildpack are built in Docker containers based on the Heroku stack image.

 ## Configuration

-File `dockerenv.default` contains a list of required env vars; most of these have default values defined in `Dockerfile`. You can copy this file to a location outside the buildpack and modify it with the values you desire and pass its location with `--env-file`, or pass the env vars to `docker run` using `--env`.
+In order to publish binaries AWS credentials must be passed to the build container.
+If you are testing only the build (ie: `bob build`), these are optional.

-Out of the box, each `Dockerfile` has the correct values predefined for `S3_BUCKET`, `S3_PREFIX`, and `S3_REGION`. If you're building your own packages, you'll likely want to change `S3_BUCKET` and `S3_PREFIX` to match your info. Instead of setting `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` into that file, you may also pass them to `docker run` through the environment, or explicitly using `--env`, in order to prevent accidental commits of credentials.
+In addition, unless you are building the official binaries for Heroku (which use the defaults
+specified in each `Dockerfile`), you will need to override `S3_BUCKET` and `S3_PREFIX` to
+match your own S3 bucket/use case.

-### Passing AWS credentials to the container
+If you only need to set AWS credentials, you can do so by setting the environment variables
+`AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` before calling the make commands.

-If you want to deploy packages and thus need to pass `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY`, you can either pass them explicitly, through your environment, or through an env file.
+For example:

-#### Passing credentials explicitly
+```bash
+set +o history # Disable bash history
+export AWS_ACCESS_KEY_ID=...
+export AWS_SECRET_ACCESS_KEY=...
+set -o history # Re-enable bash history
+make ...
+```

-    docker run --rm -ti -e AWS_ACCESS_KEY_ID=... -e AWS_SECRET_ACCESS_KEY=... heroku-python-build-heroku-18 bash
+If you need to override the default S3 bucket, or would prefer not to use credentials via
+environment variables, then you need to instead use a Docker env file like so:

-#### Passing credentials through  the environment
+1. Copy the `builds/dockerenv.default` env file to a location outside the buildpack repository.
+2. Edit the new file, adding at a minimum the values for the variables
+   `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY` (see Docker
+   [env-file documentation](https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e---env---env-file)).
+3. Pass the path of the file to the make commands using `ENV_FILE`. For example:

-The two environment variables `AWS_ACCESS_KEY_ID`and `AWS_SECRET_ACCESS_KEY` are defined in `builds/dockerenv.default`, without values. This will cause Docker to "forward" values for these variables from the current environment, so you can pass them in:
+   ```bash
+   make ... ENV_FILE=~/.dockerenv.python-buildpack
+   ```

-    AWS_ACCESS_KEY_ID=... AWS_SECRET_ACCESS_KEY=... docker run --rm -ti --env-file=builds/dockerenv.default heroku-python-build-heroku-18 bash
+## Launching an interactive build environment

-or
+To start an interactive version of the build environment (ideal for development) use the
+`buildenv` make target, passing in the desired `STACK` name. For example:

-    export AWS_ACCESS_KEY_ID=...
-    export AWS_SECRET_ACCESS_KEY=...
-    docker run --rm -ti --env-file=builds/dockerenv.default heroku-python-build-heroku-18 bash
+```bash
+make buildenv STACK=heroku-18
+```

-#### Passing credentials through a separate env file
+This will create the builder docker image based on the latest image for that stack, and
+then start a bash shell where you can run `bob build`, `bob deploy`, and so forth.

-This method is the easiest for users who want to build packages in their own S3 bucket, as they will have to adjust the `S3_BUCKET` and `S3_PREFIX` environment variable values anyway from their default values.
+The `builds/` directory is bind-mounted into the running container, so local build formula
+changes will appear there immediately without the need to rebuild the image.

-For this method, it is important to keep the credentials file in a location outside the buildpack, so that your credentials aren't accidentally committed. Copy `builds/dockerenv.default` **to a safe location outside the buildpack directory**, and insert your values for `AWS_ACCESS_KEY_ID`and `AWS_SECRET_ACCESS_KEY`.
+## Bulk deploying runtimes

-    docker run --rm -ti --env-file=../SOMEPATHOUTSIDE/s3.env heroku-python-build-heroku-18 bash
+When a new Python version is released, binaries have to be generated for multiple stacks.
+To automate this, use the `deploy-runtimes` make target, which will ensure the builder
+image is up to date, and then run `bob deploy` for each runtime-stack combination.
+
+The build formula name(s) are passed using `RUNTIMES`, like so:
+
+```bash
+make deploy-runtimes RUNTIMES='python-X.Y.Z'
+```
+
+By default this will deploy to all supported stacks (see `STACKS` in `Makefile`),
+but this can be overridden using `STACKS`:
+
+```bash
+make deploy-runtimes RUNTIMES='python-X.Y.Z' STACKS='heroku-16 heroku-18'
+```
+
+Multiple runtimes can also be specified (useful for when adding a new stack), like so:
+
+```bash
+make deploy-runtimes RUNTIMES='python-A.B.C python-X.Y.Z' STACKS='heroku-20'
+```
+
+Note: Both `RUNTIMES` and `STACKS` are space delimited.
@@ -1,15 +1,21 @@
 FROM heroku/cedar:14

-WORKDIR /app
 ENV WORKSPACE_DIR="/app/builds" \
    S3_BUCKET="lang-python" \
    S3_PREFIX="cedar-14/" \
-    DEBIAN_FRONTEND=noninteractive \
    STACK="cedar-14"

-RUN apt-get update && apt-get install -y python-pip libsqlite3-dev realpath && rm -rf /var/lib/apt/lists/*
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        realpath \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app

 COPY requirements.txt /app/
-RUN pip install -r /app/requirements.txt
+# Can't use `--disable-pip-version-check --no-cache-dir` since not supported by Ubuntu 14.04's pip.
+RUN pip3 install -r /app/requirements.txt

 COPY . /app
@@ -1,5 +1,8 @@
+# Since no values are specified here, these variables will be read from the environment at run time:
+# https://docs.docker.com/engine/reference/commandline/run/#set-environment-variables--e---env---env-file
 AWS_ACCESS_KEY_ID
 AWS_SECRET_ACCESS_KEY
-S3_BUCKET
-S3_PREFIX
-S3_REGION
+
+# Uncomment these if you need to override the default S3 bucket and/or path prefixes.
+# S3_BUCKET
+# S3_PREFIX
@@ -1,15 +1,20 @@
 FROM heroku/heroku:16-build

-WORKDIR /app
 ENV WORKSPACE_DIR="/app/builds" \
-    S3_BUCKET="lang-python" \
+    S3_BUCKET="heroku-buildpack-python" \
    S3_PREFIX="heroku-16/" \
-    DEBIAN_FRONTEND=noninteractive \
    STACK="heroku-16"

-RUN apt-get update && apt-get install -y python-pip libsqlite3-dev && rm -rf /var/lib/apt/lists/*
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        python3-setuptools \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app

 COPY requirements.txt /app/
-RUN pip install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
+RUN pip3 install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt

 COPY . /app
@@ -1,15 +1,20 @@
 FROM heroku/heroku:18-build

-WORKDIR /app
 ENV WORKSPACE_DIR="/app/builds" \
-    S3_BUCKET="lang-python" \
+    S3_BUCKET="heroku-buildpack-python" \
    S3_PREFIX="heroku-18/" \
-    DEBIAN_FRONTEND=noninteractive \
    STACK="heroku-18"

-RUN apt-get update && apt-get install --no-install-recommends -y python-pip-whl=9.0.1-2 python-pip=9.0.1-2 python-setuptools python-wheel libsqlite3-dev && rm -rf /var/lib/apt/lists/*
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        python3-setuptools \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app

 COPY requirements.txt /app/
-RUN pip install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
+RUN pip3 install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt

 COPY . /app
@@ -0,0 +1,20 @@
+FROM heroku/heroku:20-build
+
+ENV WORKSPACE_DIR="/app/builds" \
+    S3_BUCKET="heroku-buildpack-python" \
+    S3_PREFIX="heroku-20/" \
+    STACK="heroku-20"
+
+RUN apt-get update \
+    && DEBIAN_FRONTEND=noninteractive apt-get install --no-install-recommends -y \
+        libsqlite3-dev \
+        python3-pip \
+        python3-setuptools \
+    && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+
+COPY requirements.txt /app/
+RUN pip3 install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
+
+COPY . /app
@@ -19,4 +19,4 @@ make install

 # Cleanup
 cd ..
-rm -fr sqlite
+rm -rf sqlite
@@ -13,11 +13,11 @@ dep_version=${dep_formula##*"/${dep_name}-"} # "subtract" our name from full ver
 dep_package=${dep_name}-v${dep_version} # it's always "pypy2-…"
 dep_dirname=${dep_package}-linux64
 dep_archive_name=${dep_dirname}.tar.bz2
-dep_url=https://bitbucket.org/pypy/pypy/downloads/${dep_archive_name}
+dep_url="https://downloads.python.org/pypy/${dep_archive_name}"

 echo "Building PyPy…"
 echo "${dep_url}"

-curl -L "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name
+curl -fL "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name

 ln "$OUT_PREFIX/bin/pypy" "$OUT_PREFIX/bin/python"
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy2.7
@@ -13,11 +13,11 @@ dep_version=${dep_formula##*"/${dep_name}-"} # "subtract" our name from full ver
 dep_package=${dep_name}${dep_version_prefix:-}-v${dep_version}${dep_version_suffix:-}
 dep_dirname=${dep_package}-linux64
 dep_archive_name=${dep_dirname}.tar.bz2
-dep_url=https://bitbucket.org/pypy/pypy/downloads/${dep_archive_name}
+dep_url="https://downloads.python.org/pypy/${dep_archive_name}"

 echo "Building PyPy3…"
 echo "${dep_url}"

-curl -L "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name
+curl -fL "${dep_url}" | tar jx -C "${OUT_PREFIX}" --strip-components 1 # extract to $OUT_PREFIX, drop the first directory level, which is the archive name

 ln "$OUT_PREFIX/bin/pypy3" "$OUT_PREFIX/bin/python"
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/pypy3.6
@@ -1,27 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/

-OUT_PREFIX=$1
-BIN_DIR="$(cd "$(dirname "$0")"/../.. || exit; pwd)/bin"
-export BIN_DIR
-
-# shellcheck source=bin/utils
-source "$BIN_DIR/steps/sqlite3"
-
-sqlite3_version
-echo "Setting up SQLite3 Headers for $SQLITE3_VERSION"
-sqlite3_install "$OUT_PREFIX" "$SQLITE3_VERSION" 1
-
-echo "Building Python…"
-SOURCE_TARBALL='https://python.org/ftp/python/2.7.17/Python-2.7.17.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-2.7.17 src
-cd src
-
-./configure --prefix=$OUT_PREFIX  --enable-unicode=ucs4 --with-ensurepip=no
-make
-make install
-
-# Remove unneeded test directories, similar to the official Docker Python images:
-# https://github.com/docker-library/python
-find "${OUT_PREFIX}" \( -type d -a \( -name test -o -name tests \) \) -exec rm -rf '{}' +
+source $(dirname $0)/python2
@@ -1,27 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/

-OUT_PREFIX=$1
-BIN_DIR="$(cd "$(dirname "$0")"/../.. || exit; pwd)/bin"
-export BIN_DIR
-
-# shellcheck source=bin/utils
-source "$BIN_DIR/steps/sqlite3"
-
-sqlite3_version
-echo "Setting up SQLite3 Headers for $SQLITE3_VERSION"
-sqlite3_install "$OUT_PREFIX" "$SQLITE3_VERSION" 1
-
-echo "Building Python…"
-SOURCE_TARBALL='https://python.org/ftp/python/2.7.18/Python-2.7.18.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-2.7.18 src
-cd src
-
-./configure --prefix=$OUT_PREFIX  --enable-unicode=ucs4 --with-ensurepip=no
-make
-make install
-
-# Remove unneeded test directories, similar to the official Docker Python images:
-# https://github.com/docker-library/python
-find "${OUT_PREFIX}" \( -type d -a \( -name test -o -name tests \) \) -exec rm -rf '{}' +
+source $(dirname $0)/python2
@@ -1,32 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/

-OUT_PREFIX=$1
-BIN_DIR="$(cd "$(dirname "$0")"/../.. || exit; pwd)/bin"
-export BIN_DIR
-
-# shellcheck source=bin/utils
-source "$BIN_DIR/steps/sqlite3"
-
-sqlite3_version
-echo "Setting up SQLite3 Headers for $SQLITE3_VERSION"
-sqlite3_install "$OUT_PREFIX" "$SQLITE3_VERSION" 1
-
-echo "Building Python…"
-SOURCE_TARBALL='https://python.org/ftp/python/3.7.2/Python-3.7.2.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-3.7.2 src
-cd src
-
-./configure --prefix=$OUT_PREFIX --with-ensurepip=no
-make
-make install
-
-# Remove unneeded test directories, similar to the official Docker Python images:
-# https://github.com/docker-library/python
-find "${OUT_PREFIX}" \( -type d -a \( -name test -o -name tests \) \) -exec rm -rf '{}' +
-
-# Remove spare /
-LOCATION=${OUT_PREFIX%?}
-
-ln $LOCATION/bin/python3 $LOCATION/bin/python
+source $(dirname $0)/python3
@@ -1,32 +1,4 @@
 #!/usr/bin/env bash
 # Build Path: /app/.heroku/python/

-OUT_PREFIX=$1
-BIN_DIR="$(cd "$(dirname "$0")"/../.. || exit; pwd)/bin"
-export BIN_DIR
-
-# shellcheck source=bin/utils
-source "$BIN_DIR/steps/sqlite3"
-
-sqlite3_version
-echo "Setting up SQLite3 Headers for $SQLITE3_VERSION"
-sqlite3_install "$OUT_PREFIX" "$SQLITE3_VERSION" 1
-
-echo "Building Python…"
-SOURCE_TARBALL='https://python.org/ftp/python/3.4.9/Python-3.4.9.tgz'
-curl -L $SOURCE_TARBALL | tar xz
-mv Python-3.4.9 src
-cd src
-
-./configure --prefix=$OUT_PREFIX --with-ensurepip=no
-make
-make install
-
-# Remove unneeded test directories, similar to the official Docker Python images:
-# https://github.com/docker-library/python
-find "${OUT_PREFIX}" \( -type d -a \( -name test -o -name tests \) \) -exec rm -rf '{}' +
-
-# Remove spare /
-LOCATION=${OUT_PREFIX%?}
-
-ln $LOCATION/bin/python3 $LOCATION/bin/python
+source $(dirname $0)/python3
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3
@@ -0,0 +1,4 @@
+#!/usr/bin/env bash
+# Build Path: /app/.heroku/python/
+
+source $(dirname $0)/python3
@@ -1,5 +0,0 @@
-#!/usr/bin/env bash
-
-sudo apt-get -qq update
-sudo apt-get install software-properties-common
-curl --fail --retry 3 --retry-delay 1 --connect-timeout 3 --max-time 30 https://cli-assets.heroku.com/install-ubuntu.sh | sh
@@ -14,9 +14,9 @@ case "$choice" in
  * ) exit 1;;
 esac

-originMaster=$(git rev-parse origin/master)
-echo "Tagging commit $originMaster with $newVersion... "
-git tag "$newVersion" "${originMaster:?}"
+originMain=$(git rev-parse origin/main)
+echo "Tagging commit $originMain with $newVersion... "
+git tag "$newVersion" "${originMain:?}"
 git push origin refs/tags/$newVersion

 heroku buildpacks:publish "$BP_NAME" "$newVersion"
@@ -31,7 +31,7 @@ if [ $(git tag | grep -q latest-version) ]; then
    echo "Updating latest-version tag"
    git tag -d latest-version
    git push origin :latest-version
-    git tag latest-version "${originMaster:?}"
+    git tag latest-version "${originMain:?}"
    git push --tags
 fi

@@ -1,5 +1,5 @@
 ---
 - - "./repos/python/python-getting-started"
-  - master
+  - main
 - - "./repos/python/python_default"
  - ca947f69027b2a30be5d26f9a42f25e54f4d7a1a
@@ -1,3 +1,6 @@
+# Dependencies for generating/publishing Python binaries.
+bob-builder==0.0.19
+
+# Sub-dependencies of bob-builder.
+boto==2.49.0
 docopt==0.6.2
-bob-builder==0.0.17
-boto==2.48.0
@@ -1 +0,0 @@
-python-3.6.6
@@ -6,4 +6,4 @@ verify_ssl = true
 requests = "*"

 [requires]
-python_full_version = "3.6.3"
+python_full_version = "3.7.8"
@@ -1,24 +1,11 @@
 {
    "_meta": {
        "hash": {
-            "sha256": "22a052f4d1cfe6518b2f236fe45c3208c587a9ab1323bdd390632e27278b541e"
-        },
-        "host-environment-markers": {
-            "implementation_name": "cpython",
-            "implementation_version": "3.6.3",
-            "os_name": "posix",
-            "platform_machine": "x86_64",
-            "platform_python_implementation": "CPython",
-            "platform_release": "16.7.0",
-            "platform_system": "Darwin",
-            "platform_version": "Darwin Kernel Version 16.7.0: Thu Jun 15 17:36:27 PDT 2017; root:xnu-3789.70.16~2/RELEASE_X86_64",
-            "python_full_version": "3.6.3",
-            "python_version": "3.6",
-            "sys_platform": "darwin"
+            "sha256": "8a36860f0f9cb55716222098062cea5c5e0f8127cafb9d0c694de327bac9fbc0"
        },
        "pipfile-spec": 6,
        "requires": {
-            "python_full_version": "3.6.3"
+            "python_full_version": "3.7.8"
        },
        "sources": [
            {
@@ -1 +1 @@
-pypy2.7-7.2.0
+pypy2.7-7.3.2
@@ -0,0 +1 @@
+pypy2.7-7.3.1
@@ -1 +1 @@
-pypy3.6-7.2.0
+pypy3.6-7.3.2
@@ -0,0 +1 @@
+pypy3.6-7.3.1
@@ -1 +0,0 @@
-requests
@@ -1 +0,0 @@
-python-2.7.99
@@ -1 +0,0 @@
-requests
@@ -1 +0,0 @@
-flask
@@ -1 +0,0 @@
-python-3.4.99
@@ -1 +0,0 @@
-flask
@@ -1 +1 @@
-python-3.5.9
+python-3.5.10
@@ -1 +0,0 @@
-flask
@@ -1 +0,0 @@
-python-3.5.99
@@ -1 +0,0 @@
-flask
@@ -1 +1 @@
-python-3.6.8
+python-3.6.12
@@ -1 +0,0 @@
-flask
@@ -1 +0,0 @@
-python-3.6.99
@@ -1 +0,0 @@
-requests
@@ -1 +1 @@
-python-3.6.7
+python-3.6.11
@@ -1 +1 @@
-python-3.7.2
+python-3.7.9
@@ -1 +0,0 @@
-flask
@@ -1 +0,0 @@
-python-3.7.99
@@ -1 +0,0 @@
-requests
@@ -1 +1 @@
-python-3.7.1
+python-3.7.8
@@ -1 +1 @@
-python-3.8.2
+python-3.8.6
@@ -1 +0,0 @@
-flask
@@ -1 +0,0 @@
-requests
@@ -1 +1 @@
-python-3.8.0
+python-3.8.5
@@ -0,0 +1 @@
+python-3.9.0
@@ -0,0 +1 @@
+python-3.9.0
@@ -1 +0,0 @@
-flask
@@ -21,16 +21,13 @@ testGEOS() {
  local env_dir="$(mktmpdir)"
  echo '1' > "${env_dir}/BUILD_WITH_GEO_LIBRARIES"
  compile 'geos' '' "${env_dir}"
-  assertCaptured "geos"
-  assertCapturedSuccess
-}
-
-testGEOSDeprecation() {
-  local env_dir="$(mktmpdir)"
-  echo '1' > "${env_dir}/BUILD_WITH_GEO_LIBRARIES"
-  compile 'geos' '' "${env_dir}"
-  assertCaptured " !     The GDAL, GEOS and PROJ binaries and BUILD_WITH_GEO_LIBRARIES functonality are now deprecated.
- !     An alternative buildpack to enable GDAL, GEOS and PROJ use is available here - https://github.com/heroku/heroku-geo-buildpack"
+  if [[ $STACK == "heroku-20" ]]; then
+    assertCaptured " !     The GDAL, GEOS and PROJ binaries and BUILD_WITH_GEO_LIBRARIES functonality is not supported on Heroku-20."
+  else
+    assertCaptured " !     The GDAL, GEOS and PROJ binaries and BUILD_WITH_GEO_LIBRARIES functonality are now deprecated."
+  fi
+  # This should assertCapturedError on Heroku-20, but the test doesn't actually
+  # install anything that uses GEOS so succeeds (see W-8145375)
  assertCapturedSuccess
 }

@@ -43,7 +40,9 @@ testNLTK() {
  echo 'ignore::RuntimeWarning' > "${env_dir}/PYTHONWARNINGS"
  compile 'nltk' '' "${env_dir}"
  assertCaptured "[nltk_data] Downloading package city_database" "STD_ERR"
-  assertCapturedSuccess
+  # Can't use `assertCapturedSuccess` since the NLTK downloader outputs all
+  # progress/status messages to stderr (W-8146040).
+  assertCapturedSuccessWithStdErr
 }

 testPsycopg2() {
@@ -53,17 +52,16 @@ testPsycopg2() {
 }

 testPysqlite() {
+  # pysqlite does not support Python 3 (since the sqlite3 stdlib can be used there),
+  # so we have to test with Python 2, which we've not made available for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
+  fi
  compile "pysqlite"
  assertCaptured "pysqlite"
  assertCapturedSuccess
 }

-testSqliteInstall() {
-  compile "pythonDefault"
-  assertNotCaptured "Sqlite3 failed to install."
-  assertCapturedSuccess
-}
-
 testCffi() {
  compile "cffi"
  assertCaptured "cffi"
@@ -33,7 +33,9 @@ testStackChange() {
 testSetupPy() {
  compile "setup-py"
  assertCaptured "maya"
-  assertCapturedSuccess
+  # Can't use `assertCapturedSuccess` since stderr contains:
+  # "cp: cannot stat '/tmp/build_*/requirements.txt': No such file or directory" (W-7924941)
+  assertCapturedSuccessWithStdErr
 }

 testStandardRequirements() {
@@ -44,30 +46,49 @@ testStandardRequirements() {

 testPipenv() {
  compile "pipenv"
-  assertCaptured "Installing pip 9.0.2, setuptools 39.0.1 and wheel 0.34.2"
-  assertCapturedSuccess
+  assertCaptured "Installing pip 9.0.2, setuptools 47.1.1 and wheel 0.34.2"
+  # Can't use `assertCapturedSuccess` since stderr contains:
+  # "cp: cannot stat '/tmp/build_*/requirements.txt': No such file or directory" (W-7924941)
+  assertCapturedSuccessWithStdErr
 }

 testPipenvLock() {
  compile "pipenv-lock"
-  assertCapturedSuccess
+  # Can't use `assertCapturedSuccess` since stderr contains:
+  # "cp: cannot stat '/tmp/build_*/requirements.txt': No such file or directory" (W-7924941)
+  assertCapturedSuccessWithStdErr
 }

-testPipenvVersion() {
+testPipenvPythonVersion3_6() {
  compile "pipenv-version"
-  assertCaptured $DEFAULT_PYTHON_VERSION
-  assertCapturedSuccess
+  assertCaptured "Installing ${LATEST_36}"
+  # Can't use `assertCapturedSuccess` since stderr contains:
+  # "cp: cannot stat '/tmp/build_*/requirements.txt': No such file or directory" (W-7924941)
+  assertCapturedSuccessWithStdErr
 }

-testPipenvVersion2() {
+testPipenvPythonVersion2_7() {
+  # Python 2.7 is EOL, so it has not been built for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
+  fi
  compile "pipenv-version2"
-  assertCaptured $LATEST_27
-  assertCapturedSuccess
+  assertCaptured "Installing ${LATEST_27}"
+  # Can't use `assertCapturedSuccess` since stderr contains:
+  # "cp: cannot stat '/tmp/build_*/requirements.txt': No such file or directory" (W-7924941)
+  assertCapturedSuccessWithStdErr
 }
-testPipenvFullVersion() {
+
+testPipenvPythonFullVersion() {
+  # Python 3.7+ requires newer libssl than is present on Cedar-14.
+  if [[ "${STACK}" = "cedar-14" ]]; then
+    return
+  fi
  compile "pipenv-full-version"
-  assertCaptured "3.6.3"
-  assertCapturedSuccess
+  assertCaptured "3.7.8"
+  # Can't use `assertCapturedSuccess` since stderr contains:
+  # "cp: cannot stat '/tmp/build_*/requirements.txt': No such file or directory" (W-7924941)
+  assertCapturedSuccessWithStdErr
 }

 testNoRequirements() {
@@ -95,6 +116,7 @@ testHooks() {
  local expected_env_vars=(
    _
    BIN_DIR
+    BPLOG_PREFIX
    BUILD_DIR
    BUILDPACK_LOG_FILE
    CACHE_DIR
@@ -108,14 +130,15 @@ testHooks() {
    LIBRARY_PATH
    OLDPWD
    PATH
+    PIP_NO_PYTHON_VERSION_WARNING
    PKG_CONFIG_PATH
    PROFILE_PATH
    PWD
    PYTHONUNBUFFERED
+    S3_BASE_URL
    SHLVL
    SOME_APP_CONFIG_VAR
    STACK
-    VENDOR_URL
  )
  if [[ "${STACK}" == "cedar-14" || "${STACK}" == "heroku-16" ]]; then
    # Remove "OLDPWD" from expected_env_vars since for bash <4.4 it's not exported to subshells:
@@ -4,219 +4,254 @@
 # shellcheck source=bin/default_pythons
 source "bin/default_pythons"

-testPythonDefault() {
-  updateVersion "pythonDefault" $DEFAULT_PYTHON_VERSION
-  compile "pythonDefault"
-  assertCaptured $DEFAULT_PYTHON_VERSION
+testPythonVersionUnspecified() {
+  compile "python_version_unspecified"
+  assertCaptured "Installing ${DEFAULT_PYTHON_VERSION}"
  assertNotCaptured "security update"
-  assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
+  assertCaptured "Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2"
  assertCaptured "Installing SQLite3"
  assertCapturedSuccess
 }

-testPython2() {
-    updateVersion "python2" $LATEST_27
-    echo $LATEST_27 > "runtime.txt"
-    compile "python2"
-    assertCaptured $LATEST_27
-    if [[ $(date "+%Y") > "2019" ]]; then
-      assertCaptured "python-2-7-eol-faq";
-    else
-      assertNotCaptured "python-2-7-eol-faq";
-    fi
-    assertNotCaptured "security update"
-    assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
-    assertCaptured "Installing SQLite3"
-    assertCapturedSuccess
+testPython2_7() {
+  # Python 2.7 is EOL, so it has not been built for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
+  fi
+  compile "python2"
+  assertCaptured "Installing ${LATEST_27}"
+  assertCaptured "python-2-7-eol-faq";
+  assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.1.1, setuptools 44.1.1 and wheel 0.34.2"
+  assertCaptured "Installing SQLite3"
+  assertCapturedSuccess
 }

-testPython2_warn() {
-    compile "python2_warn"
-    assertCaptured "python-2.7.15"
-    if [[ $(date "+%Y") > "2019" ]]; then
-      assertCaptured "python-2-7-eol-faq";
-    else
-      assertNotCaptured "python-2-7-eol-faq";
-    fi
-    assertCaptured "Only the latest version"
-    assertCaptured "Installing SQLite3"
-    assertCapturedSuccess
-}
-
-testPython2_fail() {
-    compile "python2_fail"
-    assertCaptured "Aborting"
-    assertCapturedError
+testPython2_7_warn() {
+  # Python 2.7 is EOL, so it has not been built for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
+  fi
+  compile "python2_warn"
+  assertCaptured "Installing python-2.7.15"
+  assertCaptured "python-2-7-eol-faq";
+  assertCaptured "Only the latest version"
+  assertCaptured "${LATEST_27}"
+  assertCapturedSuccess
 }

 testPython3_4() {
-  compile "python3_4"
-  assertCaptured $LATEST_34
-  assertNotCaptured "security update"
-  assertCaptured "Installing pip 19.1.1, setuptools 39.0.1 and wheel 0.33.6"
-  # if cedar 14 and legacy binaries, fail. if cedar 14 and staging, succeed.
-  if [[ ! -n $USE_STAGING_BINARIES ]] && [[ $STACK == "cedar-14" ]]; then
-      assertCapturedError
-# if heroku 18 and legacy binaries, succeed. if heroku 18 and staging, fail.
-  elif [[ -n $USE_STAGING_BINARIES ]] && [[ $STACK == "heroku-18" ]]; then
-      assertCapturedError
-  else
-#   all else succeed
-    assertCapturedSuccess
+  # Python 3.4 is EOL, so it has not been built for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
  fi
+  compile "python3_4"
+  assertCaptured "Installing ${LATEST_34}"
+  assertNotCaptured "security update"
+  assertCaptured "Installing pip 19.1.1, setuptools 43.0.0 and wheel 0.33.6"
+  assertCaptured "Installing SQLite3"
+  # Can't use `assertCapturedSuccess` since Pip outputs a Python 3.4 EOL warning to stderr,
+  # and the newest Pip that works on Python 3.4 doesn't support `PIP_NO_PYTHON_VERSION_WARNING`.
+  assertCapturedSuccessWithStdErr
 }

 testPython3_4_warn() {
-  compile "python3_4_warn"
-  assertCaptured "python-3.4.9"
-  assertCaptured "security update!"
-# if heroku 18 and legacy binaries, succeed. if heroku 18 and staging, fail.
-  if [[ -n $USE_STAGING_BINARIES ]] && [[ $STACK == "heroku-18" ]]; then
-      assertCapturedError
-  else
-#   all else succeed
-    assertCapturedSuccess
+  # Python 3.4 is EOL, so it has not been built for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
  fi
-}
-
-testPython3_4_fail() {
-    compile "python3_4_fail"
-    assertCaptured "Aborting"
-    assertCapturedError
+  compile "python3_4_warn"
+  assertCaptured "Installing python-3.4.9"
+  assertCaptured "security update!"
+  assertCaptured "${LATEST_34}"
+  # Can't use `assertCapturedSuccess` since Pip outputs a Python 3.4 EOL warning to stderr,
+  # and the newest Pip that works on Python 3.4 doesn't support `PIP_NO_PYTHON_VERSION_WARNING`.
+  assertCapturedSuccessWithStdErr
 }

 testPython3_5() {
+  # Python 3.5 is EOL, so it has not been built for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
+  fi
  compile "python3_5"
-  assertCaptured $LATEST_35
+  assertCaptured "Installing ${LATEST_35}"
  assertNotCaptured "security update"
-  assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
+  assertCaptured "Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2"
  assertCaptured "Installing SQLite3"
  assertCapturedSuccess
 }

 testPython3_5_warn() {
+  # Python 3.5 is EOL, so it has not been built for Heroku-20.
+  if [[ $STACK == "heroku-20" ]]; then
+    return
+  fi
  compile "python3_5_warn"
-  assertCaptured "python-3.5.6"
+  assertCaptured "Installing python-3.5.6"
  assertCaptured "security update!"
+  assertCaptured "${LATEST_35}"
  assertCapturedSuccess
 }

-testPython3_5_fail() {
-    compile "python3_5_fail"
-    assertCaptured "Aborting"
-    assertCapturedError
-}
-
 testPython3_6() {
-  updateVersion "python3_6" $LATEST_36
  compile "python3_6"
-  assertCaptured $LATEST_36
+  assertCaptured "Installing ${LATEST_36}"
  assertNotCaptured "security update"
-  assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
+  assertCaptured "Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2"
  assertCaptured "Installing SQLite3"
  assertCapturedSuccess
 }

 testPython3_6_warn() {
  compile "python3_6_warn"
-  assertCaptured "python-3.6.7"
+  assertCaptured "Installing python-3.6.11"
  assertCaptured "security update!"
+  assertCaptured "${LATEST_36}"
+  assertCapturedSuccess
+}
+
+testPython3_7() {
+  # Python 3.7+ requires newer libssl than is present on Cedar-14.
+  if [[ "${STACK}" = "cedar-14" ]]; then
+    return
+  fi
+  compile "python3_7"
+  assertCaptured "Installing ${LATEST_37}"
+  assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2"
  assertCaptured "Installing SQLite3"
  assertCapturedSuccess
 }

-testPython3_6_fail() {
-    compile "python3_6_fail"
-    assertCaptured "Aborting"
-    assertCapturedError
-}
-
-testPython3_7() {
-  updateVersion "python3_7" $LATEST_37
-  compile "python3_7"
-  if [[ $STACK = "cedar-14" ]]; then
-    assertCapturedError
-  else
-    assertNotCaptured "security update"
-    assertCaptured $LATEST_37
-    assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
-    assertCaptured "Installing SQLite3"
-    assertCapturedSuccess
-  fi
-}
-
 testPython3_7_warn() {
+  # Python 3.7+ requires newer libssl than is present on Cedar-14.
+  if [[ "${STACK}" = "cedar-14" ]]; then
+    return
+  fi
  compile "python3_7_warn"
-  if [[ $STACK = "cedar-14" ]]; then
-    assertCapturedError
-  else
-    assertCaptured "python-3.7.1"
-    assertCaptured "security update!"
-    assertCaptured "Installing SQLite3"
-    assertCapturedSuccess
-  fi
-}
-
-testPython3_7_fail() {
-  compile "python3_7_fail"
-  assertCaptured "Aborting"
-  assertCapturedError
-}
-
-testPython3_7_warn() {
-  compile "python3_8_warn"
-  if [[ $STACK = "cedar-14" ]]; then
-    assertCapturedError
-  else
-    assertCaptured "python-3.8.0"
-    assertCaptured "security update!"
-    assertCaptured "Installing SQLite3"
-    assertCapturedSuccess
-  fi
+  assertCaptured "Installing python-3.7.8"
+  assertCaptured "security update!"
+  assertCaptured "${LATEST_37}"
+  assertCapturedSuccess
 }

 testPython3_8() {
-  updateVersion "python3_8" $LATEST_38
-  compile "python3_8"
-  if [[ $STACK = "cedar-14" ]]; then
-    assertCapturedError
-  else
-    assertNotCaptured "security update"
-    assertCaptured $LATEST_38
-    assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
-    assertCaptured "Installing SQLite3"
-    assertCapturedSuccess
+  # Python 3.7+ requires newer libssl than is present on Cedar-14.
+  if [[ "${STACK}" = "cedar-14" ]]; then
+    return
  fi
+  compile "python3_8"
+  assertCaptured "Installing ${LATEST_38}"
+  assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2"
+  assertCaptured "Installing SQLite3"
+  assertCapturedSuccess
 }

-testPython3_8_fail() {
-  compile "python3_8_fail"
+testPython3_8_warn() {
+  # Python 3.7+ requires newer libssl than is present on Cedar-14.
+  if [[ "${STACK}" = "cedar-14" ]]; then
+    return
+  fi
+  compile "python3_8_warn"
+  assertCaptured "Installing python-3.8.5"
+  assertCaptured "security update!"
+  assertCaptured "${LATEST_38}"
+  assertCapturedSuccess
+}
+
+testPython3_9() {
+  # Cedar-14 is EOL, so we're not building new major Python versions for it.
+  if [[ "${STACK}" = "cedar-14" ]]; then
+    return
+  fi
+  compile "python3_9"
+  assertCaptured "Installing ${LATEST_39}"
+  assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2"
+  assertCaptured "Installing SQLite3"
+  assertCapturedSuccess
+}
+
+testPython3_9_warn() {
+  # Cedar-14 is EOL, so we're not building new major Python versions for it.
+  if [[ "${STACK}" = "cedar-14" ]]; then
+    return
+  fi
+  # Can't test the version warning until there is at least one old version of Python 3.9.
+  if [[ "${LATEST_39}" = "python-3.9.0" ]]; then
+    return
+  fi
+  compile "python3_9_warn"
+  assertCaptured "Installing python-3.9.0"
+  assertCaptured "security update!"
+  assertCaptured "${LATEST_39}"
+  assertCapturedSuccess
+}
+
+testPythonVersionInvalid() {
+  compile "python_version_invalid"
+  assertCaptured "Requested runtime (python-3.8.99) is not available for this stack"
  assertCaptured "Aborting"
  assertCapturedError
 }

 testPypy3_6() {
  compile "pypy3_6"
-  if [[ $STACK = "cedar-14" ]]; then
-    assertCapturedError
-  else
-    assertCaptured "Installing pypy"
-    assertCaptured "$PYPY_36"
-    assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
-    assertCapturedSuccess
-  fi
+  assertCaptured "Installing ${LATEST_PYPY_36}"
+  assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.1.1, setuptools 47.1.1 and wheel 0.34.2"
+  assertCapturedSuccess
+}
+
+testPypy3_6_warn() {
+  compile "pypy3_6_warn"
+  assertCaptured "Installing pypy3.6-7.3.1"
+  assertCaptured "security update!"
+  assertCaptured "${LATEST_PYPY_36}"
+  assertCapturedSuccess
 }

 testPypy2_7() {
  compile "pypy2_7"
-  if [[ $STACK = "cedar-14" ]]; then
-    assertCapturedError
-  else
-    assertCaptured "Installing pypy"
-    assertCaptured "$PYPY_27"
-    assertCaptured "Installing pip 20.0.2, setuptools 39.0.1 and wheel 0.34.2"
-    assertCapturedSuccess
-  fi
+  assertCaptured "Installing ${LATEST_PYPY_27}"
+  assertNotCaptured "security update"
+  assertCaptured "Installing pip 20.1.1, setuptools 44.1.1 and wheel 0.34.2"
+  assertCapturedSuccess
+}
+
+testPypy2_7_warn() {
+  compile "pypy2_7_warn"
+  assertCaptured "Installing pypy2.7-7.3.1"
+  assertCaptured "security update!"
+  assertCaptured "${LATEST_PYPY_27}"
+  assertCapturedSuccess
+}
+
+testStickyPythonVersion() {
+  local cache_dir="$(mktmpdir)"
+  compile "python3_6_warn" "$cache_dir"
+  assertCaptured "Installing python-3.6.11"
+  assertCapturedSuccess
+  compile "python_version_unspecified" "$cache_dir"
+  assertNotCaptured "Installing python"
+  assertCaptured "security update!"
+  assertCapturedSuccess
+  # Whilst this file seems like an implementation detail (so something that should
+  # not be tested), we must guarantee the filename remains consistent for backwards
+  # compatibility across buildpack versions for already-built apps.
+  assertFile "python-3.6.11" ".heroku/python-version"
+}
+
+testPythonVersionChange() {
+  local cache_dir="$(mktmpdir)"
+  compile "python3_6_warn" "$cache_dir"
+  assertCaptured "Installing python-3.6.11"
+  assertCapturedSuccess
+  compile "python3_6" "$cache_dir"
+  assertCaptured "Found python-3.6.11, removing"
+  assertCapturedSuccess
 }

 pushd $(dirname 0) >/dev/null
@@ -56,11 +56,6 @@ resetCapture()
  unset rtrn # deprecated
 }

-updateVersion()
-{
-  echo "$2" > "test/fixtures/${1}/runtime.txt"
-}
-
 assertCapturedEquals()
 {
  assertEquals "$@" "$(cat ${STD_OUT})"
@@ -85,12 +80,20 @@ assertNotCaptured()
 assertCapturedSuccess()
 {
  assertEquals "Captured exit code -" "0" "${RETURN}"
-  # assertEquals "STD_ERR -" "" "$(cat ${STD_ERR})"
+  assertEquals "STD_ERR -" "" "$(cat ${STD_ERR})"

-  if [ $RETURN -ne 0 -a -z "$(cat ${STD_ERR})" ]; then
-    # Failing exit code but stderr was empty. Display stdout to help debugging.
-    cat $STD_OUT
-    echo
+  if [ $RETURN -ne 0 -o -n "$(cat ${STD_ERR})" ]; then
+    debug
+  fi
+}
+
+assertCapturedSuccessWithStdErr()
+{
+  assertEquals "Captured exit code -" "0" "${RETURN}"
+  assertNotEquals "STD_ERR -" "" "$(cat ${STD_ERR})"
+
+  if [ ${RETURN} -ne 0 ]; then
+    debug
  fi
 }

@@ -151,9 +154,14 @@ _assertContains()

 debug()
 {
-  cat $STD_OUT
-  echo '^^^^^^'
-  cat $STD_ERR
+  echo
+  echo '### STD_OUT ###'
+  cat "${STD_OUT}"
+  echo
+  echo '### STD_ERR ###'
+  cat "${STD_ERR}"
+  echo
+  echo
 }

 assertContains()
@@ -0,0 +1,195 @@
+#!/usr/bin/env bash
+
+# From:
+# https://raw.githubusercontent.com/heroku/buildpack-stdlib/v8/stdlib.sh
+
+# Buildpack defaults
+# ---------------
+
+export BUILDPACK_LOG_FILE="${BUILDPACK_LOG_FILE:-/dev/null}"
+
+# Standard Output
+# ---------------
+
+# Buildpack Steps.
+puts_step() {
+  if [[ "$*" == "-" ]]; then
+    read -r output
+  else
+    output=$*
+  fi
+  echo -e "\\e[1m\\e[36m=== $output\\e[0m"
+  unset output
+}
+
+# Buildpack Error.
+puts_error() {
+  if [[ "$*" == "-" ]]; then
+    read -r output
+  else
+    output=$*
+  fi
+  echo -e "\\e[1m\\e[31m=!= $output\\e[0m"
+}
+
+# Buildpack Warning.
+puts_warn() {
+  if [[ "$*" == "-" ]]; then
+    read -r output
+  else
+    output=$*
+  fi
+  echo -e "\\e[1m\\e[33m=!= $output\\e[0m"
+}
+
+# Is verbose set?
+is_verbose() {
+  if [[ -n $BUILDPACK_VERBOSE ]]; then
+    return 0
+  else
+    return 1
+  fi
+}
+
+# Buildpack Verbose.
+puts_verbose() {
+  if is_verbose; then
+    if [[ "$*" == "-" ]]; then
+      read -r output
+    else
+      output=$*
+    fi
+    echo "$output"
+    unset output
+  fi
+}
+
+# Buildpack Utilities
+# -------------------
+
+# Usage: $ set-env key value
+# NOTICE: Expects PROFILE_PATH & EXPORT_PATH to be set!
+set_env() {
+  # TODO: automatically create profile path directory if it doesn't exist.
+  echo "export $1=$2" >> "$PROFILE_PATH"
+  echo "export $1=$2" >> "$EXPORT_PATH"
+}
+
+# Usage: $ set-default-env key value
+# NOTICE: Expects PROFILE_PATH & EXPORT_PATH to be set!
+set_default_env() {
+  echo "export $1=\${$1:-$2}" >> "$PROFILE_PATH"
+  echo "export $1=\${$1:-$2}" >> "$EXPORT_PATH"
+}
+
+# Usage: $ un-set-env key
+# NOTICE: Expects PROFILE_PATH to be set!
+un_set_env() {
+  echo "unset $1" >> "$PROFILE_PATH"
+}
+
+# Usage: $ _env-blacklist pattern
+# Outputs a regex of default blacklist env vars.
+_env_blacklist() {
+  local regex=${1:-''}
+  if [ -n "$regex" ]; then
+    regex="|$regex"
+  fi
+  echo "^(PATH|GIT_DIR|CPATH|CPPATH|LD_PRELOAD|LIBRARY_PATH$regex)$"
+}
+
+# Usage: $ export-env ENV_DIR WHITELIST BLACKLIST
+# Exports the environment variables defined in the given directory.
+export_env() {
+  local env_dir=${1:-$ENV_DIR}
+  local whitelist=${2:-''}
+  local blacklist
+  blacklist="$(_env_blacklist "$3")"
+  if [ -d "$env_dir" ]; then
+    # Environment variable names won't contain characters affected by:
+    # shellcheck disable=SC2045
+    for e in $(ls "$env_dir"); do
+      echo "$e" | grep -E "$whitelist" | grep -qvE "$blacklist" &&
+      export "$e=$(cat "$env_dir/$e")"
+      :
+    done
+  fi
+}
+
+# Usage: $ sub-env command
+# Runs a subshell of specified command with user-provided config.
+# NOTICE: Expects ENV_DIR to be set. WHITELIST & BLACKLIST are optional.
+# Examples:
+#    WHITELIST=${2:-''}
+#    BLACKLIST=${3:-'^(GIT_DIR|PYTHONHOME|LD_LIBRARY_PATH|LIBRARY_PATH|PATH)$'}
+sub_env() {
+  (
+    # TODO: Fix https://github.com/heroku/buildpack-stdlib/issues/37
+    # shellcheck disable=SC2153
+    export_env "$ENV_DIR" "$WHITELIST" "$BLACKLIST"
+
+    "$@"
+  )
+}
+
+# Logging
+# -------
+
+# Notice: These functions expect BPLOG_PREFIX and BUILDPACK_LOG_FILE to be defined (BUILDPACK_LOG_FILE can point to /dev/null if not provided by the buildpack).
+# Example: BUILDPACK_LOG_FILE=${BUILDPACK_LOG_FILE:-/dev/null}; BPLOG_PREFIX="buildpack.go"
+
+# Returns now, in milleseconds. Useful for logging.
+# Example: $ let start=$(nowms); sleep 30; mtime "glide.install.time" "${start}"
+nowms() {
+  date +%s%3N
+}
+
+# Log arbitrary data to the logfile (e.g. a packaging file).
+# Usage: $ bplog "$(<${vendorJSON})
+bplog() {
+  echo -n "${@}" | awk 'BEGIN {printf "msg=\""; f="%s"} {gsub(/"/, "\\\"", $0); printf f, $0} {if (NR == 1) f="\\n%s" } END { print "\"" }' >> "${BUILDPACK_LOG_FILE}"
+}
+
+# Measures time elapsed for a specific build step.
+# Usage: $ let start=$(nowms); mtime "glide.install.time" "${start}"
+# https://github.com/heroku/engineering-docs/blob/master/guides/logs-as-data.md#distributions-measure
+mtime() {
+  local key="${BPLOG_PREFIX}.${1}"
+  local start="${2}"
+  local end="${3:-$(nowms)}"
+  echo "${key} ${start} ${end}" | awk '{ printf "measure#%s=%.3f\n", $1, ($3 - $2)/1000 }' >> "${BUILDPACK_LOG_FILE}"
+}
+
+# Logs a count for a specific built step.
+# Usage: $ mcount "tool.govendor"
+# https://github.com/heroku/engineering-docs/blob/master/guides/logs-as-data.md#counting-count
+mcount() {
+  local k="${BPLOG_PREFIX}.${1}"
+  local v="${2:-1}"
+  echo "count#${k}=${v}" >> "${BUILDPACK_LOG_FILE}"
+}
+
+# Logs a measure for a specific build step.
+# Usage: $ mmeasure "tool.installed_dependencies" 42
+# https://github.com/heroku/engineering-docs/blob/master/guides/logs-as-data.md#distributions-measure
+mmeasure() {
+  local k="${BPLOG_PREFIX}.${1}"
+  local v="${2}"
+  echo "measure#${k}=${v}" >> "${BUILDPACK_LOG_FILE}"
+}
+
+# Logs a unuique measurement build step.
+# Usage: $ munique "versions.count" 2.7.13
+# https://github.com/heroku/engineering-docs/blob/master/guides/logs-as-data.md#uniques-unique
+munique() {
+  local k="${BPLOG_PREFIX}.${1}"
+  local v="${2}"
+  echo "unique#${k}=${v}" >> "${BUILDPACK_LOG_FILE}"
+}
+
+# Measures when an exit path to the buildpack is reached, given a name, then exits 1.
+# Usage: $ mcount-exi "binExists"
+mcount_exit() {
+  mcount "error.${1}"
+  exit 1
+}
@@ -1,204 +0,0 @@
-#!/bin/sh
-
-# taken from
-# https://github.com/ryanbrainard/heroku-buildpack-testrunner/blob/master/lib/test_utils.sh
-
-oneTimeSetUp()
-{
-   TEST_SUITE_CACHE="$(mktemp -d ${SHUNIT_TMPDIR}/test_suite_cache.XXXX)"
-}
-
-oneTimeTearDown()
-{
-  rm -rf ${TEST_SUITE_CACHE}
-}
-
-setUp()
-{
-  OUTPUT_DIR="$(mktemp -d ${SHUNIT_TMPDIR}/output.XXXX)"
-  STD_OUT="${OUTPUT_DIR}/stdout"
-  STD_ERR="${OUTPUT_DIR}/stderr"
-  BUILD_DIR="${OUTPUT_DIR}/build"
-  CACHE_DIR="${OUTPUT_DIR}/cache"
-  mkdir -p ${OUTPUT_DIR}
-  mkdir -p ${BUILD_DIR}
-  mkdir -p ${CACHE_DIR}
-}
-
-tearDown()
-{
-  rm -rf ${OUTPUT_DIR}
-}
-
-capture()
-{
-  resetCapture
-
-  LAST_COMMAND="$@"
-
-  "$@" >${STD_OUT} 2>${STD_ERR}
-  RETURN=$?
-  rtrn=${RETURN} # deprecated
-}
-
-resetCapture()
-{
-  if [ -f ${STD_OUT} ]; then
-    rm ${STD_OUT}
-  fi
-
-  if [ -f ${STD_ERR} ]; then
-    rm ${STD_ERR}
-  fi
-
-  unset LAST_COMMAND
-  unset RETURN
-  unset rtrn # deprecated
-}
-
-detect()
-{
-  capture ${BUILDPACK_HOME}/bin/detect ${BUILD_DIR}
-}
-
-compile()
-{
-  capture ${BUILDPACK_HOME}/bin/compile ${BUILD_DIR} ${CACHE_DIR}
-}
-
-release()
-{
-  capture ${BUILDPACK_HOME}/bin/release ${BUILD_DIR}
-}
-
-assertCapturedEquals()
-{
-  assertEquals "$@" "$(cat ${STD_OUT})"
-}
-
-assertCapturedNotEquals()
-{
-  assertNotEquals "$@" "$(cat ${STD_OUT})"
-}
-
-assertCaptured()
-{
-  assertFileContains "$@" "${STD_OUT}"
-}
-
-assertNotCaptured()
-{
-  assertFileNotContains "$@" "${STD_OUT}"
-}
-
-assertCapturedSuccess()
-{
-  assertEquals "Expected captured exit code to be 0; was <${RETURN}>" "0" "${RETURN}"
-  assertEquals "Expected STD_ERR to be empty; was <$(cat ${STD_ERR})>" "" "$(cat ${STD_ERR})"
-}
-
-# assertCapturedError [[expectedErrorCode] expectedErrorMsg]
-assertCapturedError()
-{
-  if [ $# -gt 1 ]; then
-    expectedErrorCode=${1}
-    shift
-  fi
-
-  expectedErrorMsg=${1:-""}
-
-  if [ -z ${expectedErrorCode} ]; then
-    assertTrue "Expected captured exit code to be greater than 0; was <${RETURN}>" "[ ${RETURN} -gt 0 ]"
-  else
-    assertTrue "Expected captured exit code to be <${expectedErrorCode}>; was <${RETURN}>" "[ ${RETURN} -eq ${expectedErrorCode} ]"
-  fi
-
-  assertFileContains "Expected STD_OUT to contain error <${expectedErrorMsg}>" "${expectedErrorMsg}" "${STD_OUT}"
-  assertEquals       "STD_ERR should always be empty" "" "$(cat ${STD_ERR})"
-}
-
-assertAppDetected()
-{
-  expectedAppType=${1?"Must provide app type"}
-
-  assertCapturedSuccess
-  assertEquals "${expectedAppType}" "$(cat ${STD_OUT})"
-}
-
-assertNoAppDetected()
-{
-  assertEquals "1" "${RETURN}"
-  assertEquals "no" "$(cat ${STD_OUT})"
-  assertEquals "" "$(cat ${STD_ERR})"
-}
-
-_assertContains()
-{
-  if [ 5 -eq $# ]; then
-    msg=$1
-    shift
-  elif [ ! 4 -eq $# ]; then
-    fail "Expected 4 or 5 parameters; Receieved $# parameters"
-  fi
-
-  needle=$1
-  haystack=$2
-  expectation=$3
-  haystack_type=$4
-
-  case "${haystack_type}" in
-    "file") grep -q -F -e "${needle}" ${haystack} ;;
-    "text") echo "${haystack}" | grep -q -F -e "${needle}" ;;
-  esac
-
-  if [ "${expectation}" != "$?" ]; then
-    case "${expectation}" in
-      0) default_msg="Expected <${haystack}> to contain <${needle}>" ;;
-      1) default_msg="Did not expect <${haystack}> to contain <${needle}>" ;;
-    esac
-
-    fail "${msg:-${default_msg}}"
-  fi
-}
-
-assertContains()
-{
-  _assertContains "$@" 0 "text"
-}
-
-assertNotContains()
-{
-  _assertContains "$@" 1 "text"
-}
-
-assertFileContains()
-{
-  _assertContains "$@" 0 "file"
-}
-
-assertFileNotContains()
-{
-  _assertContains "$@" 1 "file"
-}
-
-command_exists () {
-    type "$1" > /dev/null 2>&1 ;
-}
-
-assertFileMD5()
-{
-  expectedHash=$1
-  filename=$2
-
-  if command_exists "md5sum"; then
-    md5_cmd="md5sum ${filename}"
-    expected_md5_cmd_output="${expectedHash}  ${filename}"
-  elif command_exists "md5"; then
-    md5_cmd="md5 ${filename}"
-    expected_md5_cmd_output="MD5 (${filename}) = ${expectedHash}"
-  else
-    fail "no suitable MD5 hashing command found on this system"
-  fi
-
-  assertEquals "${expected_md5_cmd_output}" "`${md5_cmd}`"
-}