Ignore cgi deprecation warning on CI

[perseoGI]

Changelog: omit
Docs: omit

From #17736,

Fix the WebOb warning, might need to update the test-dependency WebTest

Until Pylons/webob#437 is resolved, the best approach is to use the legacy-cgi package, which will allow Conan to run in Python environments greater than 3.12.

Edit

Recent versions of WebOb uses legacy-cgi as a substitute of cgi deprecated module since python 3.13.
This means it is safe to ignore the pytest warning complaining about cgi deprecation.

Also, updated python versions used in linux-tests.yml.

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[defnull]

Recent versions of webob already pull legacy-cgi as a dependency, and WebTest does not seem to restrict webob from beeing upgraded. This should not be necessary. (Not tested, just wondering why this is an issue here)

[memsharded]

Recent versions of webob already pull legacy-cgi as a dependency, and WebTest does not seem to restrict webob from beeing upgraded. This should not be necessary. (Not tested, just wondering why this is an issue here)

this is weird then, we don't have WebTest constrained (WebTest>=3.0.0, <4, and latest is 3.0.4), but we are still getting the warnings of webob in CI

[perseoGI]

Absolutely right, @defnull. I wasn't aware of this:

$ uv pip install webtest                                                                                                  
Resolved 7 packages in 189 ms
Installed 3 packages in 6 ms
 + legacy-cgi==2.6.2
 + webob==1.8.9
 + webtest==3.0.4

I have just added a pytest filter to avoid receiving the warning. @memsharded I believe that we willll always receive complaints about cgi usage if using Python versions earlier than 3.13, even with legacy-cgi installed. It's important to note that having the module installed doesn't guarantee that pytest won't detect this import.