message: Improve the number-of-arrays mismatch message in training_utils.py.
diff: @@ -528,9 +528,10 @@ def standardize_input_data(data,
  raise ValueError('Error when checking model ' + exception_prefix +
  ': the list of Numpy arrays that you are passing to '
  'your model is not the size the model expected. '
  - 'Expected to see ' + str(len(names)) + ' array(s), '
  - 'but instead got the following list of ' +
  - str(len(data)) + ' arrays: ' + str(data)[:200] + '...')
  + 'Expected to see ' + str(len(names)) + ' array(s), ' +
  + 'for inputs ' + str(names) + ' but instead got the '
  + 'following list of ' + str(len(data)) + ' arrays: ' +
  + str(data)[:200] + '...')
  elif len(names) > 1:
  raise ValueError('Error when checking model ' + exception_prefix +
  ': you are passing a list as input to your model, '
  