core: more explicit UnknownEntityError

src/memory/memory.py

@@ -789,7 +789,7 @@ class Memory(object):
         if not profile in self.entitiesCache:
             raise exceptions.ProfileNotInCacheError
         if not entity_jid.userhost() in self.entitiesCache[profile]:
-            raise exceptions.UnknownEntityError
+            raise exceptions.UnknownEntityError(entity_jid.userhost())
         entity_data = self.entitiesCache[profile][entity_jid.userhost()]
         if not keys_list:
             return entity_data