Update min python version from 3.6 to 3.8

[sbc100]

The reason for picking 3.8 here is that it provides all the features we currently have need of, and it available in the places we care about:

• debian/stable (bookworm): 3.11
• ubuntu/LTS (focal): 3.8
• emsdk: 3.9.2

The motivation for this change is twofold:

1. We get access to a few more python features.
2. We actually test using the version we claim to support (3.8 on ubuntu/focal in CI). Currently the claim that we support 3.6 could well be a lie. We don't do any testing on 3.6 do who knows if incompatibilities have snuck in.

Replaces: #23378
Fixes: #23387

[kripken]

What is the advantage of this?

[dschuff]

Another relevant place would still be MacOS, right? It doesn't include a Python on the system anymore but XCode command line tools (which I would expect many/most of our developers to have) includes python 3.9.6. So that would probably be ok for this too. I would also be curious to know what new things we want in Python 3.8 that aren't in 3.6.

[sbc100]

Another relevant place would still be MacOS, right? It doesn't include a Python on the system anymore but XCode command line tools (which I would expect many/most of our developers to have) includes python 3.9.6. So that would probably be ok for this too.

Does install Xcode put that python on the PATH? In any case that works for this change. I'm also generally less concerned about macOS since we include our own copy of python in emsdk for macOS.

I would also be curious to know what new things we want in Python 3.8 that aren't in 3.6.

Aside from the two small changes you see in this PR, not much I guess.

[sbc100]

What is the advantage of this?

Nothing major, just add a few more features we can use.

One problem we have today is that we don't actually test on 3.6 or 3.7 so stating that we support 3.6 could be a lie. Maybe better to set the minimum to something we actually test against?

[sbc100]

I added some rationale to the PR description. I'm also happy to just delay this until we have some better reasons..

[dschuff]

Does install Xcode put that python on the PATH? In any case that works for this change. I'm also generally less concerned about macOS since we include our own copy of python in emsdk for macOS.

Yes, it's in /usr/bin/python3 for me.

[kripken]

If the python features are worth it then I'm ok with this change. They do seem nice, if minor. What I don't have is a good idea of the risk of existing users having 3.6 installed, say in various linux distros. Do you?

[sbc100]

If the python features are worth it then I'm ok with this change. They do seem nice, if minor. What I don't have is a good idea of the risk of existing users having 3.6 installed, say in various linux distros. Do you?

Not really, I only looked at ubuntu and debian.

Perhaps I'll reach on the mailing list.

[sbc100]

I'm not sure how to generate a list of all python version from all distros, but I think using ubuntu/LTS and debian/stable as a baseline is probably good signal. Also, it should be noted that python3.8 itself (our new shiny version) is already EOL upstream: https://devguide.python.org/versions/

[dschuff]

RHEL appears to support several python versions; 3.6 is the default but 8-12 seem to be available.

[sbc100]

Interesting I googled RHEL 8 and got "In RHEL 8, Python 3.6 is the default, fully supported version of Python". I don't know if RHEL 8 is the current version though? Or if its used by the machines that ppl use to run emcc on?

[dschuff]

No idea about the latter question, I just know RHEL is a popular distribution for enterprises.
8 and 9 are currently supported (https://access.redhat.com/articles/3078) there's a 10 year support window, and I don't think we want to pin emscripten to a 10 year old version of Python; so in this case (see the link in my last post) there does seem to be packages of newer versions available in the distro, so that seems like it should be sufficient if a user can ensure that Emscripten is run with e.g. python38 rather than python3.