[staging] python38Packages.importlib-metadata: return null

[jonringer]

Motivation for this change

This is a backport, packages are discouraged not to use it

wondering if this is feasible, it's about a 280K closure size saving in a few thousand packages

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS linux)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nixpkgs-review --run "nixpkgs-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Ensured that relevant documentation is up to date
• Fits CONTRIBUTING.md.

[FRidh]

We should avoid setting something to null, but it is however convenient/pragmatic.

[jonringer]

The main issue is there's an import mismatch "importlib.metadata" vs "importlib_metada" (backport)

The saving is only ~280K, but it would still be nice to get rid of it.

[Vonfry]

This package is old, should we update it as well?

pypi: url

[jonringer]

This package is old, should we update it as well?

We should probably do that as part of a large update.

cc @FRidh did you want to do a python-unstable bump?

[FRidh]

cc @FRidh did you want to do a python-unstable bump?

"want" isn't how I would put it, but yes, I think it is about time again.

[jonringer]

"want" isn't how I would put it, but yes, I think it is about time again.

Did you want me to do it? Just so that the process is able to be done by more than one person?

[FRidh]

cc @FRidh did you want to do a python-unstable bump?

#117452

[jonringer]

importlib-metadata has been updated to backport 3.10 behavior. this is no longer relevant