code: def fail(self, message, view, type_error=False):
          
          exc_class = ConfigTypeError if type_error else ConfigValueError
          raise exc_class(
              u'{0}: {1}'.format(view.name, message)
          )
docs: Raise an exception indicating that a value cannot be
          accepted.
  
          `type_error` indicates whether the error is due to a type
          mismatch rather than a malformed value. In this case, a more
          specific exception is raised.