str(weakref) throws error `KeyError: '__name__'` if the original obj override __getattr__

class MyConfig(dict):
    def __getattr__(self, x):
        return self[x]

obj = MyConfig(offset=5)
obj_weakref = weakref.ref(obj)
str(obj_weakref)  # raise error: KeyError: '__name__'

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in __getattr__
KeyError: '__name__'