message: Fix unittest error message assertion
diff: @@ -1161,7 +1161,7 @@ class MetricTest(test.TestCase, parameterized.TestCase):
  saved_model_dir = self._save_model_dir()
  tf_save.save(model, saved_model_dir)
  - with self.assertRaisesRegex(ValueError, 'custom_objects'):
  + with self.assertRaisesRegex(ValueError, 'metric'):
  keras_load.load(saved_model_dir)
  keras_load.load(saved_model_dir, compile=False)
  