If we uploaded a CL w/o any reviewers specified, and then
ran the owners check on it (so that we had a Rietveld
issue number) we would crash in a Python assertion. This
wasn't caught in unit testing because of a limitation
in the unit test scaffolding.

TBR=maruel@chromium.org
BUG=None


Review URL: https://chromiumcodereview.appspot.com/12546003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@186454 0039d316-1c4b-4281-b951-d872f2087c98