@GrahamcOfBorg build pythonPackages.markdown

I tried running nox-review, it tried to build hundreds of packages in wip mode, and dozens in pr mode, so I cancelled it :/

This breaks octoprint. Please add a commit that overrides the markdown version used in pkgs/applications/misc/octoprint/default.nix.

This causes way too much breakage: flask-api, Nikola, pelican, ...
Therefore, we will not merge this as is but might include it in the next set of major Python upgrades.
cc @FRidh

@dotlambda I figured as much (wrt. major version -> breakage). Unfortunately, there is already a "markdown2", so we couldn't even keep v2 around as that and switch "markdown" to v3 :/

Roughly how often do these major Python upgrades occur?

Roughly how often do these major Python upgrades occur?

Usually about once a month. However, I don't expect the next one to happen this year.

I don't mind this PR staying open for a while, I'll put them into a local overlay, unless you think renaming and keeping two versions in the meantime would be a good idea?

No, having different versions of the same package within pythonPackages is never a sane thing to do because these different versions could both propagate into some package's build inputs.

I've removed this commit from python-unstable from now.