Update notes on Python Docker image

[StevenMaude]

The Python Docker image has now been split into v1 and v2 images: the v1 being the previously existing image, and v2 a newer image with upgraded Python and packages.

This week's link check flagged this up (see below for broken URLs); the documentation should be updated to reflect this. This also indicates the affected pages.

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Errors per input
Errors in docs/requesting-libraries.md

    [404] https://github.com/opensafely-core/python-docker/blob/main/requirements.in | Failed: Network error: Not Found

Errors in docs/actions-reusable.md

    [404] https://github.com/opensafely-core/python-docker/blob/main/requirements.txt | Failed: Network error: Not Found

Errors in docs/actions-scripts.md

    [404] https://github.com/opensafely-core/python-docker/blob/main/requirements.txt | Failed: Network error: Not Found

[StevenMaude]

My — possibly limited — understanding of the specific changes here are something like:

• there's a v1 image which is the old image for compatibility with old studies where users don't want to upgrade (this is still latest, again for backwards compatibility, so that existing studies using latest don't unintentionally use the v2 image)
• the v1 and v2 images now have specific versions that indicate the date and time (YYMMDDHHSS) of release (e.g. `v1.231211121504)
• the v1 image won't be updated (except for essential security fixes, maybe?); if you want newer software then use v2
• the v2 image has upgraded Python and Python packages
• breaking changes in future will result in a new major version of the image
• v1 is based on Ubuntu 20.04; v2 is based on Ubuntu 22.04
• the requirements for both images are now in v1 and v2 directories in the repository (and update the URLs)

That may not necessarily be all information that end users need to know.

I'll tag @bloodearnest in case Simon has anything to add here too.

[bloodearnest]

Hmm, the plan had been to test these first before announcing documenting, but I hadn't thought through the fact that the links would break.

We could maybe initially just point the link to the new file for now as a quick fix (it should be v1/requirements.txt - requirements.in I think is wrong?). latest still works, nothing is changed here.

Then we can do an full v1 renaming and v2 announcement at some point?

Regards the bullets points, all correct except this one:

the v1 image won't be updated (except for essential security fixes, maybe?); if you want newer software then use v2. I'm 100% sure this has been decided for sure - we may add new package to v1, but it would be unlikely. The update policy in the repo is deliberately vague on that.

[bloodearnest]

In fact, the link should probably be https://github.com/opensafely-core/python-docker/blob/main/v1/packages.md

[StevenMaude]

Thanks!

I'll update the broken links to move, and leave this issue open for us to update the advice to users.

Edit: I opened #1411 to fix the links.