In my patched version, the private popen.get_start_method gets a kwarg set_if_needed=True. popen.Popen calls that as before, so its behavior should not change, while the public get_start_method sets the kwarg to False.

I realise now that this has the side effect that get_start_method's output changes when multiprocessing has first been used, but then that reflects how the library works. Maybe this should be documented.

As for the contexts, those would be great.