message: In TPUEstimator.export_savedmodel(), if saving TPU metegraph fails, issue a warning instead so that user can still use the CPU metagraph.
diff: @@ -1968,13 +1968,18 @@ class TPUEstimator(estimator_lib.Estimator):
  input_receiver_fn_map[mode]}
  export_tags = [tag_constants.SERVING, tag_constants.TPU]
  mode = _REWRITE_FOR_INFERENCE_MODE
  - super(TPUEstimator, self)._add_meta_graph_for_mode(builder,
  + try:
  + (super(TPUEstimator, self).
  + _add_meta_graph_for_mode(builder,
  input_receiver_fn_map,
  checkpoint_path,
  strip_default_attrs,
  save_variables=False,
  mode=mode,
  - export_tags=export_tags)
  + export_tags=export_tags))
  + except Exception as error: # pylint: disable=broad-except
  + logging.warning('Saving meta graph for TPU failed: {}.'
  + .format(str(error)))
  def _call_model_fn(self, features, labels, mode, config):
  if mode == _REWRITE_FOR_INFERENCE_MODE:
  