> If we want to allow for closed {stdin, stdout, stderr}, I'm not sure
> what the semantics should be. Should sys.std{in, out, err} be None? Or a
> file object which always throws an error?

I would say it should be a *pseudo*-file object which always throws a *descriptive* error.  Note that setting sys.stdout to None makes print() do nothing rather than report an error:

>>> sys.stdout = None
>>> print('abc')

See also issue6501.