pytest: Fix up some unittests to succeed when run in one process

These tests had conditions that were only reliably true when run as an
isolated process.

BUG=chromium:1072136
TEST=`run_pytest -n 0`

Change-Id: Iadad6323c3a064686fae62d80cad0b7864c9fa2c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2156930
Tested-by: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
diff --git a/scripts/virtualenv_wrapper_unittest.py b/scripts/virtualenv_wrapper_unittest.py
index 2e8aae9..b1b79ba 100644
--- a/scripts/virtualenv_wrapper_unittest.py
+++ b/scripts/virtualenv_wrapper_unittest.py
@@ -37,8 +37,9 @@
   def testInsideVenv(self):
     """Test that we are inside a virtualenv."""
     # pylint: disable=protected-access
-    self.assertTrue(virtualenv_wrapper._IsInsideVenv(os.environ))
-
+    self.assertTrue(
+        (hasattr(sys, 'real_prefix') or
+         (hasattr(sys, 'base_prefix') and sys.base_prefix != sys.prefix)))
 
   def testVenvMarkers(self):
     """Test that the virtualenv marker functions work."""