When I run test suites I find something interesting. Even if I don't enable gui resource there are still windows flashing. The two tests are test_idle and test_tk. I think the root cause is that they both use test.support.import_module with no reason and then root.update(in _is_gui_available) is called and windows flash. Comment out root.update windows are gone. Is this a must or can we find some way to suppress this?