message: Variable order is misleading in error message.
diff: @@ -123,7 +123,7 @@ class GradientBoostedDecisionTreeClassifier(estimator.Estimator):
  learner_config.num_classes = n_classes
  elif learner_config.num_classes != n_classes:
  raise ValueError("n_classes (%d) doesn't match learner_config (%d)." %
  - (learner_config.num_classes, n_classes))
  + (n_classes, learner_config.num_classes))
  super(GradientBoostedDecisionTreeClassifier, self).__init__(
  model_fn=model.model_builder,
  params={
  