Dashboard - Add tests for api/oauth.py.
Dashboard - Add tests for api/oauth.py.

Review-Url: https://codereview.chromium.org/2973273002

benschmaus/catapult,catapult-project/catapult-csm,benschmaus/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult,catapult-project/catapult-csm,catapult-project/catapult-csm,catapult-project/catapult,catapult-project/catapult,catapult-project/catapult,benschmaus/catapult,benschmaus/catapult,catapult-project/catapult-csm,catapult-project/catapult