def METHOD_NAME(self):
    err = AssertionError('\xff')
    lines = traceback.format_exception_only(type(err), err)
    self.assertEqual(lines, ['AssertionError: \xff\n'])
    err = AssertionError(u'\xe9')
    lines = traceback.format_exception_only(type(err), err)
    self.assertEqual(lines, ['AssertionError: \\xe9\n'])