def METHOD_NAME(self, test, subtest, err):
    """Called at the end of a subtest.
    'err' is None if the subtest ended successfully, otherwise it's a
    tuple of values as returned by sys.exc_info().
    """
    # By default, we don't do anything with successful subtests, but
    # more sophisticated test results might want to record them.
    if err is not None:
        if getattr(self, 'failfast', False):
            self.stop()
        if issubclass(err[0], test.failureException):
            errors = self.failures
        else:
            errors = self.errors
        errors.append((subtest, self._exc_info_to_string(err, test)))
        self._mirrorOutput = True