rm python2 compat code

mfa/models.py

@@ -25,18 +25,15 @@ class User_Keys(models.Model):
                 {"username": self.username, "key": self.properties["key"]},
                 settings.SECRET_KEY,
             )
-        super(User_Keys, self).save(
+        super().save(
             force_insert=force_insert,
             force_update=force_update,
             using=using,
             update_fields=update_fields,
         )
 
-    def __unicode__(self):
-        return "%s -- %s" % (self.username, self.key_type)
-
     def __str__(self):
-        return self.__unicode__()
+        return "%s -- %s" % (self.username, self.key_type)
 
     class Meta:
         app_label = "mfa"