Just to add the last time isAlive was removed in favor of is_alive it was significant change enough that several libraries in Fedora packaging Python libraries and other open source code. The GitHub PR shows several projects that were affected and I linked to this PR while filing the fixes to relevant libraries. 

https://github.com/python/cpython/pull/15225

There are still new reports of the isAlive change when people try to upgrade : https://github.com/search?l=Python&o=desc&q=isalive+is%3Aissue&s=updated&state=open&type=Issues

I would request to really weigh in the cost of doing this since at one point this will cause more burden when the aliases have to be removed in future hindering Python upgrades and the change just seems to unify the casing of the method names without helping the user here.