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

Michael Foord added the comment: open shouldn't always be patched in builtins, it's much better to patch it in the specific namespace it's being called from. So the doc patch here shouldn't be applied as is. ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue28733> _______________________________________