[cloud_storage] Throws CredentialError for cloud storage stderr of form ServiceException: 401 Anonymous users does..
[cloud_storage] Throws CredentialError for cloud storage stderr of form ServiceException: 401 Anonymous users does..

There are cases users weren't sure how to authenticate cloud storage because
we did not use CredentialError for when cloud storage returns the following stderr:

"ServiceException: 401 Anonymous users does not have storage.objects.get access to object chrome-partner-telemetry/..."

BUG=catapult:#3329

Review-Url: https://codereview.chromium.org/2760873002

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