Small bugfixes in Lodel/user.py & "acl" plugin

Lodel/user.py

     @classmethod
     def identify(cls, client_infos):
         if len(cls.__methods) == 0:
-            raise RuntimeError("Not identification method registered")
+            warnings.warn("No identification methods registered")
         res = False
         for method in cls.__methods:
             ret = method(client_infos)

plugins/acl.py

 def check_anon(hook_name, caller, payload):
     if not UserContext.identity().is_identified:
         raise PermissionDenied("Anonymous user's are not allowed to get content")
+    return payload
 
 @LodelHook('leapi_update_pre')
 @LodelHook('leapi_delete_pre')
 def check_auth(hook_name, caller, payload):
     if not UserContext.identity().is_authenticated:
         raise PermissionDenied("Only authenticated user's are allowed to do that !")
+    return payload