admin: fixed sort of special privs

app/models/user.py

@@ -221,7 +221,7 @@ class Member(User):
 
     def special_privileges(self):
         """List member's special privileges."""
-        return sorted(self.special_privs)
+        return sorted(self.special_privs, key=lambda x: x.priv)
 
     def can_access_forum(self, forum):
         """Whether this member can read the forum's contents."""