pubsub_utils_unittest: add explicit chromite import

We're indirectly relying on apiclient in chromite in this module.
utils/unittest_suite.py is currently importing chromite all the
time which is updating sys.path for us.  Add the explicit import
here so we can delete that other code.  This helps reduce the
pollution until we can fix it.

BUG=chromium:1050892
TEST=autotest unittests still pass

Change-Id: I93345d487e73aec44faa22975605c53757b936fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/autotest/+/2049084
Reviewed-by: Allen Li <ayatane@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/site_utils/pubsub_utils_unittest.py b/site_utils/pubsub_utils_unittest.py
index 3c604ce..c052a9f 100644
--- a/site_utils/pubsub_utils_unittest.py
+++ b/site_utils/pubsub_utils_unittest.py
@@ -11,6 +11,9 @@
 
 import mox
 
+# TODO(crbug.com/1050892): The unittests rely on apiclient in chromite.
+import chromite  # pylint: disable=unused-import
+
 from apiclient import discovery
 from oauth2client.client import ApplicationDefaultCredentialsError
 from oauth2client.client import GoogleCredentials