Fix flask_util docstrings concerning GOOGLE_OAUTH2_CLIENT_SECRETS_FILE
Fix flask_util docstrings concerning GOOGLE_OAUTH2_CLIENT_SECRETS_FILE

fixes #497

clancychilds/oauth2client,jonparrott/oauth2client,googleapis/oauth2client,google/oauth2client,clancychilds/oauth2client,googleapis/oauth2client,jonparrott/oauth2client,google/oauth2client