storage_api: Avoid OverQuotaError from get_service_account_name

python/src/cloudstorage/storage_api.py

@@ -41,6 +41,11 @@
 from google.appengine.api import app_identity
 
 
+def _is_local_service_account():
+  service_account_name = app_identity.get_service_account_name()
+  return service_account_name == '' or service_account_name.endswith('@localhost')
+
+
 def _get_storage_api(retry_params, account_id=None):
   """Returns storage_api instance for API methods.
 
@@ -66,9 +71,8 @@ def _get_storage_api(retry_params, account_id=None):
 
   # when running local unit tests, the service account is test@localhost
   # from google.appengine.api.app_identity.app_identity_stub.APP_SERVICE_ACCOUNT_NAME
-  service_account = app_identity.get_service_account_name()
-  if (common.local_run() and not common.get_access_token()
-      and (not service_account or service_account.endswith('@localhost'))):
+  # call get_service_account_name rarely: it can raise OverQuotaException
+  if (common.local_run() and not common.get_access_token() and _is_local_service_account()):
     api.api_url = common.local_api_url()
   if common.get_access_token():
     api.token = common.get_access_token()