bpo-31452: fix asyncio.gather does not cancel tasks if one fails

[kwarunek]

Currently if one task fail asyncio.gather (without return_exception) leaves the rest of tasks pending instead of cancel them.

https://bugs.python.org/issue31452

[the-knights-who-say-ni]

Hello, and thanks for your contribution!

I'm a bot set up to make sure that the project can legally accept your contribution by verifying you have signed the PSF contributor agreement (CLA).

Unfortunately our records indicate you have not signed the CLA. For legal reasons we need you to sign this before we can look at your contribution. Please follow the steps outlined in the CPython devguide to rectify this issue.

Thanks again to your contribution and we look forward to looking at it!

[asvetlov]

@kwarunek your PR looks good but please do formal requirements: sign CLA and add news entry.

https://github.com/python/cpython/pull/3597/files#diff-33471390d839efb818436e087da26388L2224 covers the problem pretty well.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I didn't expect the Spanish Inquisition!. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

And if you don't make the requested changes, you will be poked with soft cushions!

[kwarunek]

I didn't expect the Spanish Inquisition!

[bedevere-bot]

Nobody expects the Spanish Inquisition!

@asvetlov: please review the changes made to this pull request.

[asvetlov]

LGTM

[asvetlov]

@1st1 I'll merge the PR if you have no objections

[1st1]

Will review it today

[1st1]

Want to confirm this with Guido first.

[bedevere-bot]

A Python core developer has requested some changes be made to your pull request before we can consider merging it. If you could please address their requests along with any other requests in other reviews from core developers that would be appreciated.

Once you have made the requested changes, please leave a comment on this pull request containing the phrase I didn't expect the Spanish Inquisition!. I will then notify any core developers who have left a review that you're ready for them to take another look at this pull request.

[1st1]

Closing this PR because the corresponding issue was rejected.