Upload results XML for warning stable builds

[encukou]

Would it make sense to save the JUnit result file for warnings builds, at least for stable builders on the main branch?

This would allow the dashboard to list tests that failed first, then succeeded on the re-run. If that happens in a test that isn't traditionally flaky, it would be good to investigate it.

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As for this PR, I don't think this is the proper way to do things, but, I'm not sure what would be a good way. Any pointers would be welcome.

[vstinner]

Which service is going to consume (remove) these XML files? In the past, these XML files filled the disk.

[zware]

There's a daily cronjob that removes anything from /data/www/buildbot/test-results that is a file older than 1 week. At the moment, there are 2.4GB of XML there and 43GB free, so I wouldn't expect a disk usage issue.

That said, I've never actually used these files, so I don't have much in the way of opinion on whether to upload more of them :). No objection if they're useful to someone.

[encukou]

They're used by the release status dashboard that I look at every day.
(Not that many errors are reported in the XMLs these days though. For an example, see the “AMD64 RHEL8 FIPS Only Blake2 Builtin Hash 3.11” entry, showing ValueErrors.)

There's a daily cronjob that removes anything from /data/www/buildbot/test-results that is a file older than 1 week

That's perfect :)

[vstinner]

There's a daily cronjob that removes anything from /data/www/buildbot/test-results that is a file older than 1 week

Oh ok, I'm fine with that.