Firstly, good_python is intended to be good code that does not cause any errors. Hacking it to not do that implies it is not good python. The good_python should not be used to test a rare case.
I expect to see a new test that only exercises the lines of code that changed. I think you want to create a separate example to test called bad_windowserrror_python and add a new test to TestPyflakes that verifies everything is okay.
Firstly, good_python is intended to be good code that does not cause any errors. Hacking it to not do that implies it is not good python. The good_python should not be used to test a rare case.
I expect to see a new test that only exercises the lines of code that changed. I think you want to create a separate example to test called bad_windowserrr or_python and add a new test to TestPyflakes that verifies everything is okay.