diff --git a/pipenv/_compat.py b/pipenv/_compat.py
index 8ccf025a..68d8069d 100644
--- a/pipenv/_compat.py
+++ b/pipenv/_compat.py
@@ -29,6 +29,11 @@ except ImportError:
                 _types.add(type(arg))
         return _types.pop()
 
+try:
+    from pathlib import Path
+except ImportError:
+    from pathlib2 import Path
+
 
 try:
     from weakref import finalize
@@ -51,8 +56,6 @@ if six.PY2:
     class ResourceWarning(Warning):
         pass
 
-# -*- coding=utf-8 -*-
-
 
 def pip_import(module_path, subimport=None, old_path=None):
     internal = 'pip._internal.{0}'.format(module_path)
diff --git a/pipenv/core.py b/pipenv/core.py
index 3c40da4e..b6c2790e 100644
--- a/pipenv/core.py
+++ b/pipenv/core.py
@@ -46,10 +46,12 @@ from .utils import (
     rmtree,
     split_argument,
     extract_uri_from_vcs_dep,
+    fs_str,
 )
 from ._compat import (
     TemporaryDirectory,
-    vcs
+    vcs,
+    Path
 )
 from .import pep508checker, progress
 from .environments import (
@@ -73,6 +75,7 @@ from .environments import (
     PIPENV_SHELL,
     PIPENV_PYTHON,
     PIPENV_VIRTUALENV,
+    PIPENV_CACHE_DIR,
 )
 
 # Backport required for earlier versions of Python.
@@ -1481,7 +1484,7 @@ def pip_install(
     pre = '--pre' if pre else ''
     quoted_pip = which_pip(allow_global=allow_global)
     quoted_pip = escape_grouped_arguments(quoted_pip)
-    upgrade_strategy = '--upgrade --upgrade-strategy=only-if-needed' if selective_upgrade else ''
+    upgrade_strategy = '--upgrade --upgrade-strategy=to-satisfy-only' if selective_upgrade else ''
     pip_command = '{0} install {4} {5} {6} {7} {3} {1} {2} --exists-action w'.format(
         quoted_pip,
         install_reqs,
@@ -1494,11 +1497,23 @@ def pip_install(
     )
     if verbose:
         click.echo('$ {0}'.format(pip_command), err=True)
-    c = delegator.run(pip_command, block=block)
+    cache_dir = Path(PIPENV_CACHE_DIR)
+    pip_config = {
+        'PIP_CACHE_DIR': fs_str(cache_dir.as_posix()),
+        'PIP_WHEEL_DIR': fs_str(cache_dir.joinpath('wheels').as_posix()),
+        'PIP_DESTINATION_DIR': fs_str(cache_dir.joinpath('pkgs').as_posix()),
+    }
+    c = delegator.run(pip_command, block=block, env=pip_config)
     return c
 
 
 def pip_download(package_name):
+    cache_dir = Path(PIPENV_CACHE_DIR)    
+    pip_config = {
+        'PIP_CACHE_DIR': fs_str(cache_dir.as_posix()),
+        'PIP_WHEEL_DIR': fs_str(cache_dir.joinpath('wheels').as_posix()),
+        'PIP_DESTINATION_DIR': fs_str(cache_dir.joinpath('pkgs').as_posix()),
+    }
     for source in project.sources:
         cmd = '{0} download "{1}" -i {2} -d {3}'.format(
             escape_grouped_arguments(which_pip()),
@@ -1506,7 +1521,7 @@ def pip_download(package_name):
             source['url'],
             project.download_location,
         )
-        c = delegator.run(cmd)
+        c = delegator.run(cmd, env=pip_config)
         if c.return_code == 0:
             break
 
diff --git a/pipenv/patched/notpip/_internal/pep425tags.py b/pipenv/patched/notpip/_internal/pep425tags.py
index bea31585..4205f6e0 100644
--- a/pipenv/patched/notpip/_internal/pep425tags.py
+++ b/pipenv/patched/notpip/_internal/pep425tags.py
@@ -10,10 +10,7 @@ import sysconfig
 import warnings
 from collections import OrderedDict
 
-try:
-    import pip._internal.utils.glibc
-except ImportError:
-    import pip.utils.glibc
+import pipenv.patched.notpip._internal.utils.glibc
 
 logger = logging.getLogger(__name__)
 
@@ -157,7 +154,7 @@ def is_manylinux1_compatible():
         pass
 
     # Check glibc version. CentOS 5 uses glibc 2.5.
-    return pip._internal.utils.glibc.have_compatible_glibc(2, 5)
+    return pipenv.patched.notpip._internal.utils.glibc.have_compatible_glibc(2, 5)
 
 
 def get_darwin_arches(major, minor, machine):
diff --git a/pipenv/patched/piptools/repositories/pypi.py b/pipenv/patched/piptools/repositories/pypi.py
index 6355f959..c435be07 100644
--- a/pipenv/patched/piptools/repositories/pypi.py
+++ b/pipenv/patched/piptools/repositories/pypi.py
@@ -4,6 +4,7 @@ from __future__ import (absolute_import, division, print_function,
 
 import hashlib
 import os
+import sys
 from contextlib import contextmanager
 from shutil import rmtree
 
@@ -20,14 +21,17 @@ from .._compat import (
     SafeFileCache,
 )
 
-from notpip._vendor.packaging.requirements import InvalidRequirement
+from notpip._vendor.packaging.requirements import InvalidRequirement, Requirement
+from notpip._vendor.packaging.version import Version, InvalidVersion, parse as parse_version
+from notpip._vendor.packaging.specifiers import SpecifierSet
 from notpip._vendor.pyparsing import ParseException
 
 from ..cache import CACHE_DIR
 from pipenv.environments import PIPENV_CACHE_DIR
 from ..exceptions import NoCandidateFound
-from ..utils import (fs_str, is_pinned_requirement, lookup_table,
-                     make_install_requirement)
+from ..utils import (fs_str, is_pinned_requirement, lookup_table, as_tuple, key_from_req,
+                     make_install_requirement, format_requirement, dedup)
+
 from .base import BaseRepository
 
 
@@ -159,7 +163,13 @@ class PyPIRepository(BaseRepository):
         if ireq.editable:
             return ireq  # return itself as the best match
 
-        all_candidates = self.find_all_candidates(ireq.name)
+        py_version = parse_version(os.environ.get('PIP_PYTHON_VERSION', str(sys.version_info[:3])))
+        all_candidates = []
+        for c in self.find_all_candidates(ireq.name):
+            if c.requires_python and not SpecifierSet(c.requires_python).contains(py_version):
+                continue
+            all_candidates.append(c)
+
         candidates_by_version = lookup_table(all_candidates, key=lambda c: c.version, unique=True)
         try:
             matching_versions = ireq.specifier.filter((candidate.version for candidate in all_candidates),
@@ -188,21 +198,33 @@ class PyPIRepository(BaseRepository):
             raise TypeError('Expected pinned InstallRequirement, got {}'.format(ireq))
 
         def gen(ireq):
-            if self.DEFAULT_INDEX_URL in self.finder.index_urls:
+            if self.DEFAULT_INDEX_URL not in self.finder.index_urls:
+                return
 
-                url = 'https://pypi.org/pypi/{0}/json'.format(ireq.req.name)
-                r = self.session.get(url)
+            url = 'https://pypi.org/pypi/{0}/json'.format(ireq.req.name)
+            releases = self.session.get(url).json()['releases']
 
-                # TODO: Latest isn't always latest.
-                latest = list(r.json()['releases'].keys())[-1]
-                if str(ireq.req.specifier) == '=={0}'.format(latest):
-                    latest_url = 'https://pypi.org/pypi/{0}/{1}/json'.format(ireq.req.name, latest)
-                    latest_requires = self.session.get(latest_url)
-                    for requires in latest_requires.json().get('info', {}).get('requires_dist', {}):
-                        i = InstallRequirement.from_line(requires)
+            matches = [
+                r for r in releases
+                if '=={0}'.format(r) == str(ireq.req.specifier)
+            ]
+            if not matches:
+                return
 
-                        if 'extra' not in repr(i.markers):
-                            yield i
+            release_requires = self.session.get(
+                'https://pypi.org/pypi/{0}/{1}/json'.format(
+                    ireq.req.name, matches[0],
+                ),
+            ).json()
+            try:
+                requires_dist = release_requires['info']['requires_dist']
+            except KeyError:
+                return
+
+            for requires in requires_dist:
+                i = InstallRequirement.from_line(requires)
+                if 'extra' not in repr(i.markers):
+                    yield i
 
         try:
             if ireq not in self._json_dep_cache:
@@ -226,7 +248,6 @@ class PyPIRepository(BaseRepository):
 
         return json_results
 
-
     def get_legacy_dependencies(self, ireq):
         """
         Given a pinned or an editable InstallRequirement, returns a set of
@@ -245,7 +266,13 @@ class PyPIRepository(BaseRepository):
                     setup_requires = self.finder.get_extras_links(
                         dist.get_metadata_lines('requires.txt')
                     )
-            except TypeError:
+                # HACK: Sometimes the InstallRequirement doesn't properly get
+                # these values set on it during the resolution process. It's
+                # difficult to pin down what is going wrong. This fixes things.
+                ireq.version = dist.version
+                ireq.project_name = dist.project_name
+                ireq.req = dist.as_requirement()
+            except (TypeError, ValueError):
                 pass
 
         if ireq not in self._dependencies_cache:
diff --git a/pipenv/project.py b/pipenv/project.py
index 986b7683..bf86b10c 100644
--- a/pipenv/project.py
+++ b/pipenv/project.py
@@ -20,7 +20,7 @@ except ImportError:
     from pathlib2 import Path
 
 from .cmdparse import Script
-from .vendor.requirementslib import Requirement
+from .vendor.requirementslib.requirements import Requirement
 from .utils import (
     atomic_open_for_write,
     mkdir_p,
@@ -728,8 +728,8 @@ class Project(object):
         # Read and append Pipfile.
         p = self.parsed_pipfile
         # Don't re-capitalize file URLs or VCSs.
-        package = Requirement.from_line(package_name)
-        converted = first(package.as_pipfile().values())
+        package = Requirement.from_line(package_name.strip())
+        _, converted = package.pipfile_entry
         key = 'dev-packages' if dev else 'packages'
         # Set empty group if it doesn't exist yet.
         if key not in p:
diff --git a/pipenv/utils.py b/pipenv/utils.py
index ce95ce52..27ce9d30 100644
--- a/pipenv/utils.py
+++ b/pipenv/utils.py
@@ -1,20 +1,20 @@
 # -*- coding: utf-8 -*-
 import errno
+import logging
 import os
 import re
-import hashlib
-import tempfile
-import sys
 import shutil
-import logging
+import sys
+
 import crayons
 import parse
 import six
 import stat
 import warnings
-from click import echo as click_echo
 
+from click import echo as click_echo
 from first import first
+
 try:
     from weakref import finalize
 except ImportError:
@@ -28,9 +28,10 @@ except ImportError:
             def detach(self):
                 return False
 
+logging.basicConfig(level=logging.ERROR)
+
 from time import time
 
-logging.basicConfig(level=logging.ERROR)
 try:
     from urllib.parse import urlparse
 except ImportError:
@@ -48,7 +49,7 @@ from .pep508checker import lookup
 from .environments import (
     PIPENV_MAX_ROUNDS,
     PIPENV_CACHE_DIR,
-    PIPENV_MAX_RETRIES
+    PIPENV_MAX_RETRIES,
 )
 
 try:
@@ -219,8 +220,8 @@ def prepare_pip_source_args(sources, pip_args=None):
 def actually_resolve_reps(
     deps, index_lookup, markers_lookup, project, sources, verbose, clear, pre, req_dir=None
 ):
-    from .patched.notpip._internal import basecommand, req
-    from .patched.notpip._vendor import requests as pip_requests
+    from .patched.notpip._internal import basecommand
+    from .patched.notpip._internal.req import parse_requirements
     from .patched.notpip._internal.exceptions import DistributionNotFound
     from .patched.notpip._vendor.requests.exceptions import HTTPError
     from pipenv.patched.piptools.resolver import Resolver
@@ -228,7 +229,7 @@ def actually_resolve_reps(
     from pipenv.patched.piptools.scripts.compile import get_pip_command
     from pipenv.patched.piptools import logging as piptools_logging
     from pipenv.patched.piptools.exceptions import NoCandidateFound
-    from ._compat import TemporaryDirectory
+    from ._compat import TemporaryDirectory, NamedTemporaryFile
 
     class PipCommand(basecommand.Command):
         """Needed for pip-tools."""
@@ -240,54 +241,51 @@ def actually_resolve_reps(
         req_dir = TemporaryDirectory(suffix='-requirements', prefix='pipenv-')
         cleanup_req_dir = True
     for dep in deps:
-        if dep:
-            if dep.startswith('-e '):
-                constraint = req.InstallRequirement.from_editable(
-                    dep[len('-e '):]
-                )
-            else:
-                fd, t = tempfile.mkstemp(
-                    prefix='pipenv-', suffix='-requirement.txt', dir=req_dir.name
-                )
-                with os.fdopen(fd, 'w') as f:
-                    f.write(dep)
-                constraint = [
-                    c for c in req.parse_requirements(t, session=pip_requests)
-                ][
-                    0
-                ]
-            # extra_constraints = []
-            if ' -i ' in dep:
-                index_lookup[constraint.name] = project.get_source(
-                    url=dep.split(' -i ')[1]
-                ).get(
-                    'name'
-                )
-            if constraint.markers:
-                markers_lookup[constraint.name] = str(
-                    constraint.markers
-                ).replace(
-                    '"', "'"
-                )
-            constraints.append(constraint)
+        if not dep:
+            continue
+        url = None
+        if ' -i ' in dep:
+            dep, url = dep.split(' -i ')
+        req = Requirement.from_line(dep)
+
+        # req.as_line() is theoratically the same as dep, but is guarenteed to
+        # be normalized. This is safer than passing in dep.
+        # TODO: Stop passing dep lines around; just use requirement objects.
+        constraints.append(req.as_line())
+        # extra_constraints = []
+
+        if url:
+            index_lookup[req.name] = project.get_source(url=url).get('name')
+        if req.markers:
+            markers_lookup[req.name] = req.markers.replace('"', "'")
+    constraints_file = None
     pip_command = get_pip_command()
     pip_args = []
     if sources:
         pip_args = prepare_pip_source_args(sources, pip_args)
+    with NamedTemporaryFile(mode='w', prefix='pipenv-', suffix='-constraints.txt', dir=req_dir.name, delete=False) as f:
+        if sources:
+            requirementstxt_sources = ' '.join(pip_args).replace(' --', '\n--')
+            f.write(u'{0}\n'.format(requirementstxt_sources))
+        f.write(u'\n'.join([_constraint for _constraint in constraints]))
+        constraints_file = f.name
     if verbose:
         print('Using pip: {0}'.format(' '.join(pip_args)))
+    pip_args = pip_args.extend(['--cache-dir', PIPENV_CACHE_DIR])
     pip_options, _ = pip_command.parse_args(pip_args)
     session = pip_command._build_session(pip_options)
     pypi = PyPIRepository(
-        pip_options=pip_options, use_json=False, session=session
+        pip_options=pip_options, use_json=True, session=session
     )
     if verbose:
         logging.log.verbose = True
         piptools_logging.log.verbose = True
     resolved_tree = set()
-
     resolver = Resolver(
-        constraints=constraints,
+        constraints=parse_requirements(
+            constraints_file,
+            finder=pypi.finder, session=pypi.session, options=pip_options,
+        ),
         repository=pypi,
         clear_caches=clear,
         prereleases=pre,
@@ -1130,7 +1128,7 @@ def extract_uri_from_vcs_dep(dep):
     return None
 
 
-def install_or_update_vcs(vcs_obj, src_dir, name, rev=None):    
+def install_or_update_vcs(vcs_obj, src_dir, name, rev=None):
     target_dir = os.path.join(src_dir, name)
     target_rev = vcs_obj.make_rev_options(rev)
     if not os.path.exists(target_dir):
@@ -1139,50 +1137,100 @@ def install_or_update_vcs(vcs_obj, src_dir, name, rev=None):
     return vcs_obj.get_revision(target_dir)
 
 
-def get_vcs_deps(project, pip_freeze=None, which=None, verbose=False, clear=False, pre=False, allow_global=False, dev=False):
-    from ._compat import vcs
-    section = 'vcs_dev_packages' if dev else 'vcs_packages'
+def get_vcs_deps(
+    project,
+    pip_freeze=None,
+    which=None,
+    verbose=False,
+    clear=False,
+    pre=False,
+    allow_global=False,
+    dev=False,
+):
+    from .patched.notpip._internal.vcs import VcsSupport
+
+    section = "vcs_dev_packages" if dev else "vcs_packages"
     lines = []
     lockfiles = []
     try:
         packages = getattr(project, section)
     except AttributeError:
         return [], []
-    vcs_registry = vcs()
+    src_dir = Path(
+        os.environ.get("PIP_SRC", os.path.join(project.virtualenv_location, "src"))
+    )
+    src_dir.mkdir(mode=0o775, exist_ok=True)
+    vcs_registry = VcsSupport
     vcs_uri_map = {
-        extract_uri_from_vcs_dep(v): {'name': k, 'ref': v.get('ref')}
+        extract_uri_from_vcs_dep(v): {"name": k, "ref": v.get("ref")}
         for k, v in packages.items()
     }
-    for line in pip_freeze.strip().split('\n'):
+    for line in pip_freeze.strip().split("\n"):
         # if the line doesn't match a vcs dependency in the Pipfile,
         # ignore it
         _vcs_match = first(_uri for _uri in vcs_uri_map.keys() if _uri in line)
         if not _vcs_match:
             continue
 
-        pipfile_name = vcs_uri_map[_vcs_match]['name']
-        pipfile_rev = vcs_uri_map[_vcs_match]['ref']
-        src_dir = os.environ.get('PIP_SRC', os.path.join(project.virtualenv_location, 'src'))
-        mkdir_p(src_dir)
+        pipfile_name = vcs_uri_map[_vcs_match]["name"]
+        pipfile_rev = vcs_uri_map[_vcs_match]["ref"]
+        pipfile_req = Requirement.from_pipfile(pipfile_name, [], packages[pipfile_name])
         names = {pipfile_name}
-        _pip_uri = line.lstrip('-e ')
-        backend_name = str(_pip_uri.split('+', 1)[0])
-        backend = vcs_registry._registry[first(b for b in vcs_registry if b == backend_name)]
-        __vcs = backend(url=_pip_uri)
-
+        backend = vcs_registry()._registry.get(pipfile_req.vcs)
+        # TODO: Why doesn't pip freeze list 'git+git://' formatted urls?
+        if line.startswith("-e ") and not "{0}+".format(pipfile_req.vcs) in line:
+            line = line.replace("-e ", "-e {0}+".format(pipfile_req.vcs))
         installed = Requirement.from_line(line)
+        __vcs = backend(url=installed.req.uri)
+
         names.add(installed.normalized_name)
         locked_rev = None
         for _name in names:
-            locked_rev = install_or_update_vcs(__vcs, src_dir, _name, rev=pipfile_rev)
+            locked_rev = install_or_update_vcs(
+                __vcs, src_dir.as_posix(), _name, rev=pipfile_rev
+            )
         if installed.is_vcs:
             installed.req.ref = locked_rev
             lockfiles.append({pipfile_name: installed.pipfile_entry[1]})
-        pipfile_srcdir = os.path.join(src_dir, pipfile_name)
-        lockfile_srcdir = os.path.join(src_dir, installed.normalized_name)
+        pipfile_srcdir = (src_dir / pipfile_name).as_posix()
+        lockfile_srcdir = (src_dir / installed.normalized_name).as_posix()
         lines.append(line)
         if os.path.exists(pipfile_srcdir):
-            lockfiles.extend(venv_resolve_deps(['-e {0}'.format(pipfile_srcdir)], which=which, verbose=verbose, project=project, clear=clear, pre=pre, allow_global=allow_global))
+            lockfiles.extend(
+                venv_resolve_deps(
+                    ["-e {0}".format(pipfile_srcdir)],
+                    which=which,
+                    verbose=verbose,
+                    project=project,
+                    clear=clear,
+                    pre=pre,
+                    allow_global=allow_global,
+                )
+            )
         else:
-            lockfiles.extend(venv_resolve_deps(['-e {0}'.format(lockfile_srcdir)], which=which, verbose=verbose, project=project, clear=clear, pre=pre, allow_global=allow_global))
+            lockfiles.extend(
+                venv_resolve_deps(
+                    ["-e {0}".format(lockfile_srcdir)],
+                    which=which,
+                    verbose=verbose,
+                    project=project,
+                    clear=clear,
+                    pre=pre,
+                    allow_global=allow_global,
+                )
+            )
     return lines, lockfiles
+
+
+def fs_str(string):
+    """Encodes a string into the proper filesystem encoding
+
+    Borrowed from pip-tools
+    """
+    if isinstance(string, str):
+        return string
+    assert not isinstance(string, bytes)
+    return string.encode(_fs_encoding)
+
+
+_fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()
diff --git a/pipenv/vendor/requirementslib/__init__.py b/pipenv/vendor/requirementslib/__init__.py
index ef4d46a8..11e09675 100644
--- a/pipenv/vendor/requirementslib/__init__.py
+++ b/pipenv/vendor/requirementslib/__init__.py
@@ -1,4 +1,4 @@
 # -*- coding=utf-8 -*-
-__version__ = "0.0.4"
+__version__ = "0.0.7.dev0"
 
 from .requirements import Requirement
diff --git a/pipenv/vendor/requirementslib/requirements.py b/pipenv/vendor/requirementslib/requirements.py
index 04e561c6..4b167ca8 100644
--- a/pipenv/vendor/requirementslib/requirements.py
+++ b/pipenv/vendor/requirementslib/requirements.py
@@ -8,7 +8,7 @@ import requirements
 import six
 from attr import attrs, attrib, Factory, validators
 import attr
-from ._compat import Link, path_to_url, _strip_extras
+from ._compat import Link, path_to_url, _strip_extras, InstallRequirement, Wheel
 from distlib.markers import Evaluator
 from packaging.markers import Marker, InvalidMarker
 from packaging.specifiers import SpecifierSet, InvalidSpecifier
@@ -30,6 +30,11 @@ try:
 except ImportError:
     from pathlib2 import Path
 
+try:
+    from urllib.parse import urlparse
+except ImportError:
+    from urlparse import urlparse
+
 HASH_STRING = " --hash={0}"
 
 
@@ -261,7 +266,7 @@ class NamedRequirement(BaseRequirement):
 
     @property
     def pipfile_part(self):
-        pipfile_dict = attr.asdict(self, filter=_filter_none)
+        pipfile_dict = attr.asdict(self, filter=_filter_none).copy()
         if "version" not in pipfile_dict:
             pipfile_dict["version"] = "*"
         name = pipfile_dict.pop("name")
@@ -301,20 +306,23 @@ class FileRequirement(BaseRequirement):
     @link.default
     def get_link(self):
         target = "{0}#egg={1}".format(self.uri, self.name)
-        return Link(target)
+        link = Link(target)
+        if link.is_wheel and self._has_hashed_name:
+            self.name = os.path.basename(Wheel(link.path).name)
+        return link
 
     @req.default
     def get_requirement(self):
-        base = "{0}".format(self.link)
-        req = first(requirements.parse(base))
+        prefix = "-e " if self.editable else ""
+        line = "{0}{1}".format(prefix, self.link.url)
+        req = first(requirements.parse(line))
+        if self.path and self.link and self.link.scheme.startswith("file"):
+            req.local_file = True
+            req.path = self.path
+            req.uri = None
+            self._uri_scheme = "file"
         if self.editable:
             req.editable = True
-        if self.link and self.link.scheme.startswith("file"):
-            if self.path:
-                req.path = self.path
-                req.local_file = True
-                self._uri_scheme = "file"
-                req.uri = None
         req.link = self.link
         return req
 
@@ -338,15 +346,24 @@ class FileRequirement(BaseRequirement):
                 "Supplied requirement is not installable: {0!r}".format(line)
             )
 
-        if is_valid_url(line):
+        if is_valid_url(line) and not is_installable_file(line):
             link = Link(line)
         else:
-            _path = Path(line)
-            link = Link(_path.absolute().as_uri())
-            if _path.is_absolute() or _path.as_posix() == ".":
-                path = _path.as_posix()
+            if is_valid_url(line):
+                parsed = urlparse(line)
+                link = Link('{0}'.format(line))
+                if parsed.scheme == "file":
+                    path = Path(parsed.path).absolute().as_posix()
+                    if get_converted_relative_path(path) == ".":
+                        path = "."
+                    line = path
             else:
-                path = get_converted_relative_path(line)
+                _path = Path(line)
+                link = Link(_path.absolute().as_uri())
+                if _path.is_absolute() or _path.as_posix() == ".":
+                    path = _path.as_posix()
+                else:
+                    path = get_converted_relative_path(line)
         arg_dict = {
             "path": path,
             "uri": link.url_without_fragment,
@@ -571,6 +588,7 @@ class Requirement(object):
     editable = attrib(default=None)
     hashes = attrib(default=Factory(list), converter=list)
     extras = attrib(default=Factory(list))
+    _ireq = None
     _INCLUDE_FIELDS = ("name", "markers", "index", "editable", "hashes", "extras")
 
     @name.default
@@ -749,6 +767,17 @@ class Requirement(object):
     def pipfile_entry(self):
         return self.as_pipfile().copy().popitem()
 
+    @property
+    def ireq(self):
+        if not self._ireq:
+            ireq_line = self.as_line()
+            if ireq_line.startswith("-e "):
+                ireq_line = ireq_line[len("-e "):]
+                self._ireq = InstallRequirement.from_editable(ireq_line)
+            else:
+                self._ireq = InstallRequirement.from_line(ireq_line)
+        return self._ireq
+
 
 def _extras_to_string(extras):
     """Turn a list of extras into a string"""
diff --git a/pipenv/vendor/requirementslib/utils.py b/pipenv/vendor/requirementslib/utils.py
index b9358a35..5302630a 100644
--- a/pipenv/vendor/requirementslib/utils.py
+++ b/pipenv/vendor/requirementslib/utils.py
@@ -35,7 +35,10 @@ def is_vcs(pipfile_entry):
 
 def get_converted_relative_path(path, relative_to=os.curdir):
     """Given a vague relative path, return the path relative to the given location"""
-    return os.path.join(".", os.path.relpath(path, start=relative_to))
+    relpath = os.path.relpath(path, start=relative_to)
+    if os.name == 'nt':
+        return os.altsep.join([".", relpath])
+    return os.path.join(".", relpath)
 
 
 def multi_split(s, split):
@@ -73,6 +76,10 @@ def is_installable_file(path):
         else:
             return False
 
+    parsed = urlparse(path)
+    if parsed.scheme == 'file':
+        path = parsed.path
+
     if not os.path.exists(os.path.abspath(path)):
         return False
 
@@ -90,7 +97,7 @@ def is_installable_file(path):
 def is_valid_url(url):
     """Checks if a given string is an url"""
     pieces = urlparse(url)
-    return all([pieces.scheme, pieces.netloc])
+    return all([pieces.scheme, any([pieces.netloc, pieces.path])])
 
 
 def pep423_name(name):
diff --git a/tasks/vendoring/__init__.py b/tasks/vendoring/__init__.py
index 9bd14dee..4b64b818 100644
--- a/tasks/vendoring/__init__.py
+++ b/tasks/vendoring/__init__.py
@@ -468,7 +468,10 @@ def generate_patch(ctx, package_path, patch_description, base='HEAD'):
     pkg = Path(package_path)
     if len(pkg.parts) != 2 or pkg.parts[0] not in ('vendor', 'patched'):
         raise ValueError('example usage: generate-patch patched/pew some-description')
-    patch_fn = '{0}-{1}.patch'.format(pkg.parts[1], patch_description)
+    if patch_description:
+        patch_fn = '{0}-{1}.patch'.format(pkg.parts[1], patch_description)
+    else:
+        patch_fn = '{0}.patch'.format(pkg.parts[1])
     command = 'git diff {base} -p {root} > {out}'.format(
         base=base,
         root=Path('pipenv').joinpath(pkg),
diff --git a/tasks/vendoring/patches/patched/_post-pip-update-pep425tags.patch b/tasks/vendoring/patches/patched/_post-pip-update-pep425tags.patch
index 70ccd170..ebebe17e 100644
--- a/tasks/vendoring/patches/patched/_post-pip-update-pep425tags.patch
+++ b/tasks/vendoring/patches/patched/_post-pip-update-pep425tags.patch
@@ -1,16 +1,25 @@
 diff --git a/pipenv/patched/notpip/_internal/pep425tags.py b/pipenv/patched/notpip/_internal/pep425tags.py
-index bea31585..9e9609f3 100644
+index bea31585..4205f6e0 100644
 --- a/pipenv/patched/notpip/_internal/pep425tags.py
 +++ b/pipenv/patched/notpip/_internal/pep425tags.py
-@@ -11,9 +11,9 @@ import warnings
+@@ -10,10 +10,7 @@ import sysconfig
+ import warnings
  from collections import OrderedDict
  
- try:
+-try:
 -    import pip._internal.utils.glibc
-+    import pipenv.patched.notpip._internal.utils.glibc
- except ImportError:
+-except ImportError:
 -    import pip.utils.glibc
-+    import pipenv.patched.notpip.utils.glibc
++import pipenv.patched.notpip._internal.utils.glibc
  
  logger = logging.getLogger(__name__)
  
+@@ -157,7 +154,7 @@ def is_manylinux1_compatible():
+         pass
+ 
+     # Check glibc version. CentOS 5 uses glibc 2.5.
+-    return pip._internal.utils.glibc.have_compatible_glibc(2, 5)
++    return pipenv.patched.notpip._internal.utils.glibc.have_compatible_glibc(2, 5)
+ 
+ 
+ def get_darwin_arches(major, minor, machine):
diff --git a/tasks/vendoring/patches/patched/piptools.patch b/tasks/vendoring/patches/patched/piptools.patch
index 6beaad8e..fe2c46d8 100644
--- a/tasks/vendoring/patches/patched/piptools.patch
+++ b/tasks/vendoring/patches/patched/piptools.patch
@@ -19,10 +19,18 @@ index 4e6174c..75f9b49 100644
  # NOTE
  # We used to store the cache dir under ~/.pip-tools, which is not the
 diff --git a/pipenv/patched/piptools/repositories/pypi.py b/pipenv/patched/piptools/repositories/pypi.py
-index 1c4b943..8320e14 100644
+index 1c4b943..aae0122 100644
 --- a/pipenv/patched/piptools/repositories/pypi.py
 +++ b/pipenv/patched/piptools/repositories/pypi.py
-@@ -15,10 +15,16 @@ from .._compat import (
+@@ -4,6 +4,7 @@ from __future__ import (absolute_import, division, print_function,
+ 
+ import hashlib
+ import os
++import sys
+ from contextlib import contextmanager
+ from shutil import rmtree
+ 
+@@ -15,13 +16,22 @@ from .._compat import (
      Wheel,
      FAVORITE_HASH,
      TemporaryDirectory,
@@ -32,15 +40,23 @@ index 1c4b943..8320e14 100644
 +    SafeFileCache,
  )
  
-+from pip._vendor.packaging.requirements import InvalidRequirement
++from pip._vendor.packaging.requirements import InvalidRequirement, Requirement
++from pip._vendor.packaging.version import Version, InvalidVersion, parse as parse_version
++from pip._vendor.packaging.specifiers import SpecifierSet
 +from pip._vendor.pyparsing import ParseException
 +
  from ..cache import CACHE_DIR
 +from pipenv.environments import PIPENV_CACHE_DIR
  from ..exceptions import NoCandidateFound
- from ..utils import (fs_str, is_pinned_requirement, lookup_table,
-                      make_install_requirement)
-@@ -37,6 +43,40 @@ except ImportError:
+-from ..utils import (fs_str, is_pinned_requirement, lookup_table,
+-                     make_install_requirement)
++from ..utils import (fs_str, is_pinned_requirement, lookup_table, as_tuple, key_from_req,
++                     make_install_requirement, format_requirement, dedup)
++
+ from .base import BaseRepository
+ 
+ 
+@@ -37,6 +47,40 @@ except ImportError:
      from pip.wheel import WheelCache
  
  
@@ -81,7 +97,7 @@ index 1c4b943..8320e14 100644
  class PyPIRepository(BaseRepository):
      DEFAULT_INDEX_URL = PyPI.simple_url
  
-@@ -46,10 +86,11 @@ class PyPIRepository(BaseRepository):
+@@ -46,10 +90,11 @@ class PyPIRepository(BaseRepository):
      config), but any other PyPI mirror can be used if index_urls is
      changed/configured on the Finder.
      """
@@ -95,7 +111,7 @@ index 1c4b943..8320e14 100644
  
          index_urls = [pip_options.index_url] + pip_options.extra_index_urls
          if pip_options.no_index:
-@@ -74,11 +115,15 @@ class PyPIRepository(BaseRepository):
+@@ -74,11 +119,15 @@ class PyPIRepository(BaseRepository):
          # of all secondary dependencies for the given requirement, so we
          # only have to go to disk once for each requirement
          self._dependencies_cache = {}
@@ -113,9 +129,18 @@ index 1c4b943..8320e14 100644
  
      def freshen_build_caches(self):
          """
-@@ -116,8 +161,11 @@ class PyPIRepository(BaseRepository):
+@@ -114,10 +163,19 @@ class PyPIRepository(BaseRepository):
+         if ireq.editable:
+             return ireq  # return itself as the best match
  
-         all_candidates = self.find_all_candidates(ireq.name)
+-        all_candidates = self.find_all_candidates(ireq.name)
++        py_version = parse_version(os.environ.get('PIP_PYTHON_VERSION', str(sys.version_info[:3])))
++        all_candidates = []
++        for c in self.find_all_candidates(ireq.name):
++            if c.requires_python and not SpecifierSet(c.requires_python).contains(py_version):
++                continue
++            all_candidates.append(c)
++
          candidates_by_version = lookup_table(all_candidates, key=lambda c: c.version, unique=True)
 -        matching_versions = ireq.specifier.filter((candidate.version for candidate in all_candidates),
 +        try:
@@ -126,7 +151,7 @@ index 1c4b943..8320e14 100644
  
          # Reuses pip's internal candidate sort key to sort
          matching_candidates = [candidates_by_version[ver] for ver in matching_versions]
-@@ -126,11 +174,60 @@ class PyPIRepository(BaseRepository):
+@@ -126,11 +184,71 @@ class PyPIRepository(BaseRepository):
          best_candidate = max(matching_candidates, key=self.finder._candidate_sort_key)
  
          # Turn the candidate into a pinned InstallRequirement
@@ -147,21 +172,33 @@ index 1c4b943..8320e14 100644
 +            raise TypeError('Expected pinned InstallRequirement, got {}'.format(ireq))
 +
 +        def gen(ireq):
-+            if self.DEFAULT_INDEX_URL in self.finder.index_urls:
++            if self.DEFAULT_INDEX_URL not in self.finder.index_urls:
++                return
 +
-+                url = 'https://pypi.org/pypi/{0}/json'.format(ireq.req.name)
-+                r = self.session.get(url)
++            url = 'https://pypi.org/pypi/{0}/json'.format(ireq.req.name)
++            releases = self.session.get(url).json()['releases']
 +
-+                # TODO: Latest isn't always latest.
-+                latest = list(r.json()['releases'].keys())[-1]
-+                if str(ireq.req.specifier) == '=={0}'.format(latest):
-+                    latest_url = 'https://pypi.org/pypi/{0}/{1}/json'.format(ireq.req.name, latest)
-+                    latest_requires = self.session.get(latest_url)
-+                    for requires in latest_requires.json().get('info', {}).get('requires_dist', {}):
-+                        i = InstallRequirement.from_line(requires)
++            matches = [
++                r for r in releases
++                if '=={0}'.format(r) == str(ireq.req.specifier)
++            ]
++            if not matches:
++                return
 +
-+                        if 'extra' not in repr(i.markers):
-+                            yield i
++            release_requires = self.session.get(
++                'https://pypi.org/pypi/{0}/{1}/json'.format(
++                    ireq.req.name, matches[0],
++                ),
++            ).json()
++            try:
++                requires_dist = release_requires['info']['requires_dist']
++            except KeyError:
++                return
++
++            for requires in requires_dist:
++                i = InstallRequirement.from_line(requires)
++                if 'extra' not in repr(i.markers):
++                    yield i
 +
 +        try:
 +            if ireq not in self._json_dep_cache:
@@ -185,12 +222,11 @@ index 1c4b943..8320e14 100644
 +
 +        return json_results
 +
-+
 +    def get_legacy_dependencies(self, ireq):
          """
          Given a pinned or an editable InstallRequirement, returns a set of
          dependencies (also InstallRequirements, but not necessarily pinned).
-@@ -139,6 +236,18 @@ class PyPIRepository(BaseRepository):
+@@ -139,6 +257,24 @@ class PyPIRepository(BaseRepository):
          if not (ireq.editable or is_pinned_requirement(ireq)):
              raise TypeError('Expected pinned or editable InstallRequirement, got {}'.format(ireq))
  
@@ -203,13 +239,19 @@ index 1c4b943..8320e14 100644
 +                    setup_requires = self.finder.get_extras_links(
 +                        dist.get_metadata_lines('requires.txt')
 +                    )
-+            except TypeError:
++                # HACK: Sometimes the InstallRequirement doesn't properly get
++                # these values set on it during the resolution process. It's
++                # difficult to pin down what is going wrong. This fixes things.
++                ireq.version = dist.version
++                ireq.project_name = dist.project_name
++                ireq.req = dist.as_requirement()
++            except (TypeError, ValueError):
 +                pass
 +
          if ireq not in self._dependencies_cache:
              if ireq.editable and (ireq.source_dir and os.path.exists(ireq.source_dir)):
                  # No download_dir for locally available editable requirements.
-@@ -164,11 +273,14 @@ class PyPIRepository(BaseRepository):
+@@ -164,11 +300,14 @@ class PyPIRepository(BaseRepository):
                      download_dir=download_dir,
                      wheel_download_dir=self._wheel_download_dir,
                      session=self.session,
@@ -226,7 +268,7 @@ index 1c4b943..8320e14 100644
                  )
              except TypeError:
                  # Pip >= 10 (new resolver!)
-@@ -190,14 +302,44 @@ class PyPIRepository(BaseRepository):
+@@ -190,14 +329,44 @@ class PyPIRepository(BaseRepository):
                      upgrade_strategy="to-satisfy-only",
                      force_reinstall=False,
                      ignore_dependencies=False,
@@ -273,7 +315,7 @@ index 1c4b943..8320e14 100644
              reqset.cleanup_files()
          return set(self._dependencies_cache[ireq])
  
-@@ -224,17 +366,10 @@ class PyPIRepository(BaseRepository):
+@@ -224,17 +393,10 @@ class PyPIRepository(BaseRepository):
          matching_candidates = candidates_by_version[matching_versions[0]]
  
          return {