message: Check if checkpoints are avaiable in TF-TRT quantization test
diff: @@ -130,6 +130,9 @@ class QuantizationAwareTrainingMNISTTest(test_util.TensorFlowTestCase):
  # Load weights
  mnist_saver = saver.Saver()
  checkpoint_file = latest_checkpoint(model_dir)
  + if checkpoint_file is None:
  + raise ValueError('latest_checkpoint returned None. check if' +
  + 'model_dir={} is the right directory'.format(model_dir))
  mnist_saver.restore(sess, checkpoint_file)
  # Freeze
  graph_def = graph_util.convert_variables_to_constants(
  