Mach-nix alternatives

[TyberiusPrime]

With mach-nix being no longer maintained (and me not picking up this puppy),
and dream2nix not being ready for prime time (I believe),
Let's gather some alternatives for the casual visitors of this issue tracker.

To my mind mach-nix did two things:

1. 'solve python package versions' giving requirements + a date (or a pypi-debs-db version)
2. turn those python package versions into nix derivations.

My understanding of dream2nix is that it's essentially 'lockfile-to-nix', so it will cover 2.
For now, 2 is being covered nicely by poetry2nix.

For 1, I've hacked up ancient-poetry,
which will produce a poetry lock-file with no packages newer than a given date.
I think it complements poetry2nix rather nicely for my use cases.