determin virtualenv location on the run

Signed-off-by: Frost Ming <mianghong@gmail.com>

pipenv/project.py

@@ -46,6 +46,7 @@ from .environments import (
     PIPENV_TEST_INDEX,
     PIPENV_PYTHON,
     PIPENV_DEFAULT_PYTHON_VERSION,
+    PIPENV_IGNORE_VIRTUALENVS,
     is_in_virtualenv
 )
 
@@ -427,7 +428,8 @@ class Project(object):
     def virtualenv_location(self):
         # if VIRTUAL_ENV is set, use that.
         virtualenv_env = os.getenv("VIRTUAL_ENV")
-        if virtualenv_env:
+        if ("PIPENV_ACTIVE" not in os.environ and
+                not PIPENV_IGNORE_VIRTUALENVS and virtualenv_env):
             return virtualenv_env
 
         if not self._virtualenv_location:  # Use cached version, if available.

tests/integration/test_project.py

@@ -185,6 +185,7 @@ def test_include_editable_packages(PipenvInstance, pypi, testsroot, pathlib_tmpd
 @pytest.mark.project
 def test_run_in_virtualenv(PipenvInstance, pypi, virtualenv):
     with PipenvInstance(chdir=True, pypi=pypi) as p:
+        os.environ.pop("PIPENV_IGNORE_VIRTUALENVS", None)
         project = Project()
         assert project.virtualenv_location == str(virtualenv)
         c = p.pipenv("run pip install click")