The following seem like a reasonable starting point to me:

TypeError: Failed to set name on 'BadIdea' instance 'attr' in 'NotGoingToWork': 'NoneType' object is not callable

TypeError: Failed to set name on 'FaultyImplementation' instance 'attr' in 'TheoreticallyCouldWork': ZeroDivisionError: division by zero


That is, the error message format would be along the lines of:

    f"Failed to set name on {type(the_attr).__name__!r} instance {the_attr_name!r} in {class_being_defined.__name__!r}: {str(raised_exc)}"