Revert commit regarding signal reveivers

This reverts commit f71bca73.

ssoauth/apps.py

@@ -22,7 +22,7 @@ class SSOAuthConfig(AppConfig):
             else:
                 logger.warning(msg)
         # default groups
-        post_migrate.connect(self.post_migrate_callback, sender=type(self))
+        post_migrate.connect(self.post_migrate_callback, sender=self)
 
     @staticmethod
     def post_migrate_callback(*args, **kwargs):