message: Include the actual differences in error messages when api compatibility tests fail with update_goldens=False.
diff: @@ -297,6 +297,9 @@ class ApiCompatibilityTest(test.TestCase):
  file_io.write_string_to_file(
  filepath, text_format.MessageToString(actual_dict[key]))
  else:
  + # Include the actual differences to help debugging.
  + for d in diffs:
  + logging.error(' %s', d)
  # Fail if we cannot fix the test by updating goldens.
  self.fail('%d differences found between API and golden.' % diff_count)
  