Here's a patch just for Modules/signalmodule.c (and related files), based on Georg's patch, updated to apply against current default, including fixes thanks to Serhiy's review.

This include one minor doc change, since I changed the name of the second parameter to signal.pthread_kill from "signum" to "signalnum" to be consistent with the rest of the signal module. This will not break existing code since this parameter is positional-only.