Expand environment variables when loading the noxfile from provided path

nox/tasks.py

@@ -41,7 +41,10 @@ def load_nox_module(global_config):
         # Save the absolute path to the Noxfile.
         # This will inoculate it if nox changes paths because of an implicit
         # or explicit chdir (like the one below).
-        global_config.noxfile = os.path.realpath(global_config.noxfile)
+        global_config.noxfile = os.path.realpath(
+            # Be sure to expand variables
+            os.path.expandvars(global_config.noxfile)
+        )
 
         # Move to the path where the Noxfile is.
         # This will ensure that the Noxfile's path is on sys.path, and that

tests/test_sessions.py

@@ -400,7 +400,7 @@ def test__create_venv_options(self, create):
 
         create.assert_called_once_with(runner.venv)
         assert isinstance(runner.venv, nox.virtualenv.VirtualEnv)
-        assert runner.venv.interpreter is "coolpython"
+        assert runner.venv.interpreter == "coolpython"
         assert runner.venv.reuse_existing is True
 
     def make_runner_with_mock_venv(self):

tests/test_tasks.py

@@ -17,6 +17,7 @@
 import io
 import json
 import os
+import platform
 from unittest import mock
 
 import pytest
@@ -43,6 +44,20 @@ def test_load_nox_module():
     assert noxfile_module.SIGIL == "123"
 
 
+def test_load_nox_module_expandvars():
+    # Assert that variables are expanded when looking up the path to the noxfile
+    # This is particular importand in Windows when one needs to use variables like
+    # %TEMP% to point to the noxfile.py
+    with mock.patch.dict(os.environ, {"RESOURCES_PATH": RESOURCES}):
+        if platform.system().lower().startswith("win"):
+            config = argparse.Namespace(noxfile="%RESOURCES_PATH%/noxfile.py")
+        else:
+            config = argparse.Namespace(noxfile="${RESOURCES_PATH}/noxfile.py")
+        noxfile_module = tasks.load_nox_module(config)
+    assert noxfile_module.__file__ == os.path.join(RESOURCES, "noxfile.py")
+    assert noxfile_module.SIGIL == "123"
+
+
 def test_load_nox_module_not_found():
     config = argparse.Namespace(noxfile="bogus.py")
     assert tasks.load_nox_module(config) == 2

tests/test_virtualenv.py

@@ -54,7 +54,7 @@ def test_constructor_defaults(make_one):
 def test_constructor_explicit(make_one):
     venv, _ = make_one(interpreter="python3.5", reuse_existing=True)
     assert venv.location
-    assert venv.interpreter is "python3.5"
+    assert venv.interpreter == "python3.5"
     assert venv.reuse_existing is True