gh-37883: Safely skip test_resource file size tests when limits are strict

[Shrey-N]

This fixes the Standing issue #37883 where test_resource would fail on systems with file size limitations

Previous attempts (like #140872) tried to introduce massive refactoring and helper classes. Based on reviewer feedback I read there, I have tried a minimal fix

• It checks if the system's hard limit is large enough, and if the OS actually allows the limit to be modified. If not, it uses self.skipTest with an informative message rather than failing with an unhandled OSError or ValueError.
• It replaces the fragile dual try...finally resource restoration blocks with self.addCleanup(), guaranteeing that limits are reset even during a test assertion failure.

Fixes #37883

• Issue: test_resource fails when file size is limited #37883

[python-cla-bot]

All commit authors signed the Contributor License Agreement.

[Shrey-N]

I have added a news entry, though I am not sure if it's necessary or for this fix, Please let me know if I should remove it :)

[encukou]

This looks good!

We don't need a NEWS entry for a test-only change.

[Shrey-N]

@encukou Alrighty thank you, I was confused as to add it or not so thank you for clearing that up :), also I will incorporate your reviews in a second :)

[encukou]

I think you can roll back the last 4 commits.

In d21ceb8, the removed comment says:

            # Close will attempt to flush the byte we wrote
            # Restore limit first to avoid getting a spurious error

That should stay, i.e. the try/finally should go inside the with, not the other way around.

[Shrey-N]

Alright will look into it asap

[Shrey-N]

@encukou I believe everything should work now :) Sorry for the late reply

[Shrey-N]

@encukou Hi, I believe I fixed the tests that were failing from my side in this PR, I am pretty sure this time, it's not my fault :) lmk if I am to make any other changes :)

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @encukou for commit 4564e1f 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F145579%2Fmerge

If you want to schedule another build, you need to add the 🔨 test-with-buildbots label again.

[Shrey-N]

Accepted all suggestions, thanks!

[encukou]

Thank you!

[miss-islington-app]

Thanks @Shrey-N for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13.
🐍🍒⛏🤖

[miss-islington-app]

Thanks @Shrey-N for the PR, and @encukou for merging it 🌮🎉.. I'm working now to backport this PR to: 3.14.
🐍🍒⛏🤖

[miss-islington-app]

Sorry, @Shrey-N and @encukou, I could not cleanly backport this to 3.13 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 461125aaa331fe2b39452c852ee26d0161b2436e 3.13

[miss-islington-app]

Sorry, @Shrey-N and @encukou, I could not cleanly backport this to 3.14 due to a conflict.
Please backport using cherry_picker on command line.

cherry_picker 461125aaa331fe2b39452c852ee26d0161b2436e 3.14

[encukou]

We usually backport test fixes to earlier versions, but mostly to avoid conflicts in future fixes. Since there are conflicts already, I'll skip backporting.

If you need the fix in an earlier version, feel free to open a backport PR.