Bump Python version requirement?

[jeanas]

Currently, setup.cfg describes Pygments as supporting Python 3.5 and higher. This is also what CI tests. Python 3.5 went EOL in 2020 and 3.6 did the same two months ago. Perhaps it would be time to bump to 3.7 or 3.6? In particular, if it becomes at least 3.6, f-strings can be used.

[Anteru]

@birkenfeld any objections? I'm fine bumping it to 3.6, and we don't have an official policy in place. If we do bump it I'd like to add one though. Suggested wording (this would go into a future goals-non-goals document):

Pygments supports all supported Python versions as per the Python Developer's Guide. Supporting end-of-life versions is a non-goal of Pygments.

I just checked: Ubuntu 18.04 uses Python 3.6.9. That would be the only reason to support 3.6 and not go to 3.7 in my opinion, to not break old installations of Ubuntu. Debian Bullseye/stable is at Python 3.9. I could add a sentence like:

Additionally, we strive to support the current and previous LTS release of Ubuntu out of the box and their default Python versions.

In 3 months they'll ship Ubuntu 22.04 so we could drop 3.6.9. That said, I'm not sure it's worth picking one distro over another, and my personal preference would be to stick with supported versions to simplify our life. That said, we do support 3.5 and so far nobody had an issue with that, so it seemed "free", but I'm not sure what value add it's providing.

[birkenfeld]

I'd prefer to stay on 3.6 for RHEL8. I don't think there are 3.7+ features we want to have?

[jeanas]

Looking at https://docs.python.org/3/whatsnew/3.7.html, I don't see anything outstanding. 3.7 is famous for dataclasses but I don't think these are of much use to Pygments.

[Anteru]

Proposed wording:

Pygments supports all supported Python versions as per the Python Developer's Guide. Additionally, the default Python version of the latest stable version of RHEL, Ubuntu LTS, and Debian are supported, even if they're officially EOL. Supporting other end-of-life versions is a non-goal of Pygments.

That said, on CentOS 8 at least, the latest Python you can install is 3.9, but 3.6 is the default. I also tried redhat/ubi8 and that also sports newer Python releases, though 3.6 is the default there. Same for Ubuntu LTS 18.04.

[jeanas]

Would a PR to do this be welcome? (The reason for asking in the first place is that I'm preparing a series of changes where f-strings will be useful.)

[Anteru]

I'll bump it to 3.6 and add the sentence above. Then you can go and knock yourself out with "f-strings" :)

[jeanas]

Thank you!

[birkenfeld]

Great!