'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().'

def addSubTest(self, test, subtest, err):

    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
