The following code causes an assertion failure in PyErr_WriteUnraisable() (in
Python/errors.c):

class BadException(Exception):
    __module__ = None

class BadClass:
    def __del__(self):
        raise BadException

foo = BadClass()
del foo


this is because PyErr_WriteUnraisable() assumes that __module__ is a string,
and passes it to _PyUnicode_EqualToASCIIId(), which asserts it received a string.


what is the wanted behavior in such a case?
should we ignore the bad __module__ and print '<unknown>' as the module name
in the traceback?