bpo-46829: Deprecate passing a message into Future.cancel() and Task.cancel()

[asvetlov]

https://bugs.python.org/issue46829

[gvanrossum]

Please hold off on merging this until we've come to some kind of agreement on whether to deprecate .cancel(msg). See bpo-46829.

[gvanrossum]

Also, if we do this we should add deprecation markup to the docs. Search for 'method:: cancel' in asyncio-future.rst and asyncio-task.rst. Also there's a note at the very bottom of asyncio-future.rst about the difference between asyncio.Future.cancel and concurrent.futures.Future.cancel that should be deprecated.

[asvetlov]

Forgot about docs, thanks.
Sure, I'll wait for the final decision.
Just wanted to don't do it at the last moment before the feature freeze.

[asvetlov]

I've updated the doc.

[gvanrossum]

I don't know how long to wait for @cjerdonek to respond or agree.

[asvetlov]

@cjerdonek would you comment on this pull request, please?

[gvanrossum]

I'm just going to merge this. @cjerdonek, if you have a convincing argument to keep this, we can always revert this PR.

[gvanrossum]

At the core dev sprint we discussed this and decided to revert this. I'm aiming to get the reversal into 3.11.