Description of problem:
It is forbidden to remove an object that is referenced by another object. User is presented with error message after attempt to do this but the message does not say which objects reference it. If the user really needs to remove the object he needs to clear the references and where to look for them
The error message only explains why it is not possible to remove the object. It doesn't help user to make it possible.
The error should list all objects that are referencing the object that is going to be removed.