Python3.8 sphinx build failure on unstable

[jtojnar]

@stianlagstad

  ] ++ (with old-nixpkgs; [
    # Adding an old nixpkgs to get python38 and python39 working, ref
    # <https://discourse.nixos.org/t/python3-8-sphinx-build-failure-on-unstable/29102/11?u=stianlagstad>
    python38
    python39
    python310
    python311
  ]);

That is why with expression is discouraged by many people. You are probably getting python38 from with pkgs you have in the outer scope. Notice that the reply that suggested this correctly wrapped the with pkgs scope in parentheses:

@iFreilicht

environment.systemPackages = (with pkgs; [
    ...
    python310
    python311
    ...
  ]) ++

Either add the parentheses, or just use old-nixpkgs.python38 directly.

Also, if you are passing old-nixpkgs from inputs directly to specialArgs as suggested in Python3.8 sphinx build failure on unstable - #13 by iFreilicht, you are passing the whole flake, so you would have to use something like old-nixpkgs.legacyPackages.x86_64-linux.python38 in the configuration.

Or just pass only the old package set:

specialArgs = {
  old-nixpkgs = old-nixpkgs.legacyPackages.${system};
};