[py3] Fixed bad unicode test

    name = models.CharField(max_length=7)

    def __str__(self):

        # Intentionally broken (trying to insert a unicode value into a str

        # object).

        return 'Názov: %s' % self.name

        # Intentionally broken (invalid start byte in byte string).

        return b'Name\xff: %s'.decode() % self.name

class NonAutoPK(models.Model):