auth_stored_credentials.py

    def auth_stored_credentials(self, scopes=[]):
        """Authorize stored credentials."""
        # this has a dependence on oauth2client
        if not scopes:
            scopes = self.client_scopes
        try:
            parser = argparse.ArgumentParser(parents=[tools.argparser])
            parser.add_argument('args', nargs=argparse.REMAINDER)
            flags = parser.parse_args()
            flags.noauth_local_webserver = True
        except ImportError:
            flags = None
        store = FileStorage(self.credentials_file)
        credentials = store.get()
        if not credentials or credentials.invalid:
            flow = client.flow_from_clientsecrets(
                self.client_secrets_file,
                scopes,
            )
            flow.user_agent = self.app_name
            if flags:
                credentials = tools.run_flow(flow, store, flags)
            # removed support for python 2.6
            # else:  # Needed only for compatibility with Python 2.6
            #     credentials = tools.run(flow, store)
            print 'Saved credentials to ' + self.credentials_file
        return credentials