Made a PR for this

I'm not sure if this is going to be useful enough to force all contributors to deal with. Justification for a change should be on bugs.python.org and that's mentioned in the CONTRIBUTING.md guidelines. As for testing, the Travis/AppVeyor failures should communicate that. And for specifying the issue number, there's a status check for that to help communicate it.

I'll let other core devs comment, but while I appreciate what Jensen is trying to help with, I don't think the template helps enough to justify forcing every contributor to have to deal with it.

You can also bring this up on the core-workflow mailing list, Jensen, if you want to discuss it there.

> What is this pull request for?

I didn't notice so many PR without useful commit message (PR description). Not sure that it's useful.

> Include version updates if necessary.

I don't understand this part.

> Make sure you have signed the CLA agreement before continuing

We have a bot for that and the bot explains how to sign it, no?


> ### Reason to modify

I never saw such template in any other project. I'm not sure that we must require an exact format for new PR.


> ### Tests and reviews
> I have tested the code and it works.

While I run Linux and have Windows and FreeBSD VM, sometimes I'm lazy and rely on the CI. I consider that it's waste to burn CI CPUs sometimes :-) For example, it's not that easy to test a change specific to Windows on Python 2.7, but AppVeyor now runs tests for you!

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@Jensen: I feel that you have useful hints for new contributors, but I suggest you to enhance the devguide instead of using a template.

OK, since Victor has verified my thinking wasn't totally off-target, I'm going to close this.

Thanks for the idea and taking the time for the PR, Jensen. If you do want to file issues or PRs against the devguide, the repo is at https://github.com/python/devguide.