[docs] [issue28733] Show how to use mock_open in modules other that __main__

Michał Bultrowicz added the comment: One more update - I had the problem, because I was using monkeypatch.setattr() from Pytest, and assumed that it will work the same as patch(). This assumption turned out to be wrong. ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue28733> _______________________________________