When one uses a file object returned by `FileType.__call__` as a context manager, `sys.stdin`'s or `sys.stdout`'s `__exit__` will be triggered upon exit of the context, in turn calling their `close` method.

Perhaps the issue is that `sys.stdin` and `sys.stdout` have poor `__exit__` methods, but my proposal (and it's not a particularly clean one) is to override the file object's `__exit__` if it happens to be either `sys.stdin` or `sys.stdout` to simply return True when called.