Add virtualenv_wrapper target for running pytest

Skips any test that transitively imports android_build due to failures
around importing vendored oauth2client rather than the version available
in the virtualenv.

BUG=chromium:1062688, chromium:1060214
TEST=`run_pytest`
TEST=`run_tests`

Cq-Depend: chromium:2109271, chromium:2118619
Change-Id: I40168d7ce8abc03da7a6ee8e784c6892d38511c2
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2109274
Tested-by: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Greg Edelston <gredelston@google.com>
Commit-Queue: Chris McDonald <cjmcdonald@chromium.org>
diff --git a/scripts/run_pytest.py b/scripts/run_pytest.py
new file mode 100644
index 0000000..8772ff7
--- /dev/null
+++ b/scripts/run_pytest.py
@@ -0,0 +1,16 @@
+# -*- coding: utf-8 -*-
+# Copyright 2020 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Wrapper to execute pytest inside the chromite virtualenv."""
+
+from __future__ import print_function
+
+import sys
+
+import pytest  # pylint: disable=import-error
+
+
+def main(argv):
+  sys.exit(pytest.main(argv))