[python-committers] Contrib forms

As some may have been noticed, I started urging contributors more intensely to submit contributor forms before accepting their patches. I encourage all committers to do the same, for non-trivial changes.

You may wonder what changed between before and now: we (the PSF) now have a good management of the forms, thanks to them being listed in Roundup, and thanks to Pat (Campbell) keeping track of all forms that we receive. So we (the committers) are now in a position to actually verify that we have a contrib form received before deciding whether or not to commit a patch.

Regards, Martin