Update minimum supported Python to 3.9

[whimboo]

As of now the minimum supported version of Python for web-platform tests is Python 3.8. Given that this release is supported until October 2024 we should start planning to get rid of it and use at least version 3.9 which gets security updates until October 2025.

Right now such a bump would be blocked at least from Mozilla side because the wpt tests are still running on workers which have Python 3.8 installed. But over the last months newer images have been created with Python 3.10 installed and those are getting slowly rolled out. There is specifically bug 1865353 for web-platform tests.

I'm filing this as issue for now to get feedback from other vendors regarding their requirements and possible blockers. I assume that we want to keep support for all available Python versions or should we even consider bumping the minimum version to 3.10? Feedback is welcome.

CC @jgraham, @foolip, @jcscottiii, @gsnedders, @Ms2ger

[gsnedders]

I assume that we want to keep support for all available Python versions or should we even consider bumping the minimum version to 3.10?

Both the macOS Ventura and Sonoma aligned Xcode releases, Xcode 14 & 15, ship with Python 3.9 — and WebKit needs to be buildable and testable with them until support for both OSes is dropped.

[jgraham]

Apparently we need to support 3.8 for as long as Ubuntu does, which is expected to be some time in 2025.

[whimboo]

To extend on what James wrote the Ubuntu 20.04 LTS release is using Python 3.8.2 and will reach its end of life in April 2025.

[foolip]

@past can you give feedback about this for Chromium?

[past]

As far as I can tell Chromium CI is using Python 3.11. @WeizhongX can you confirm?

[WeizhongX]

Unfortunately Chromium CI is using python 3.8.

[WeizhongX]

Update: we are starting to migrate to python 3.11. So this will be fine for us once that is done.