message: Use proper iso8601 time format in log.
  Format in the previous state didn't give the timezone.
diff: @@ -253,7 +253,7 @@ def _evaluate_once(checkpoint_path,
  if isinstance(h, (_StopAfterNEvalsHook, _MultiStepStopAfterNEvalsHook)):
  h._set_evals_completed_tensor(eval_step_value) # pylint: disable=protected-access
  - logging.info('Starting evaluation at ' + time.strftime('%Y-%m-%d-%H:%M:%S',
  + logging.info('Starting evaluation at ' + time.strftime('%Y-%m-%dT%H:%M:%SZ',
  time.gmtime()))
  # Prepare the session creator.
  