def test_unixCheckerSucceedsBytes(self):
        """
        The checker works with valid L{bytes} credentials.
        """
        def _gotAvatar(username):
            self.assertEqual(username,
                             self.adminBytes.username.decode("utf-8"))
        return (self.checkerBytes
                .requestAvatarId(self.adminBytes)
                .addCallback(_gotAvatar))

        The checker works with valid L{bytes} credentials.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/cred/test/test_strcred.py