message: Fix a TypeError
  We cannot concatenate string and FailedPreConditionError
diff: @@ -132,7 +132,7 @@ def _tpu_session_context():
  An error occurred connecting or initializing your TPU.
  The session has been reset. re-run keras_to_tpu_model to create a new session.
  -""" + e)
  +""" + str(e))
  def setup_tpu_session(cluster_resolver):
  