DOC: better error message

src/caoscrawler/sync_node.py

@@ -101,9 +101,10 @@ class SyncNode:
             ):
                 raise ValueError(
                     "The SyncNode that is used with update must have an equivalent"
-                    f" identifiable. The identifiables where:\n"
-                    f"{self.identifiable.get_representation()}\n"
-                    f"and\n{other.identifiable.get_representation()}."
+                    f" identifiable. I.e. you cannot merge entities with differing identifiables"
+                    "The identifiables where:\n"
+                    f"{Identifiable._create_hashable_string(self)}\n"
+                    f"and\n{Identifiable._create_hashable_string(other)}."
                 )
 
         if other.identifiable: