Distlib not comparing version '3.10' correctly

Consider the following derivation:

{ pkgs ? import <nixpkgs> {} }:                                                         /* import all standard nix packages */

let
  mach-nix = import (
    builtins.fetchGit {
      url = "https://github.com/DavHau/mach-nix/";
      ref = "3.2.0";
    }) {

      pypiDataRev = "e723ab9fa1527957ee6d9f498ddb6fbf52f739a7";
      pypiDataSha256 = "1wxqbj8h3cgdhq69xxl7c2z7lxn8snvb5lqq5qk40bgsxp5168hp";

      python = "python38";                                                                      /* define python version */
    };

  pythonPackages = mach-nix.mkPython {                                          /* import all necessary python packages */
    requirements = ''
      cobra
      biopython
    '';
    providers = {
      "ruamel.yaml" = "nixpkgs";                                                        /* need to build this specific package from source due to cobra */
    };
  };

  RPackages = with pkgs; [                                                                      /* import all necessary R packages */
  ];

  linuxPackages = with pkgs; [                                                          /* import all necessary standard linux packages */
  ];

in

pkgs.mkShell {
  buildInputs = [ pythonPackages ] ++ RPackages ++ linuxPackages;
}

It works fine, except for the fact that I have to specify ruamel.yaml manually. If however I switch to 3.3.0, it breaks with

ERROR: Could not find a version that satisfies the requirement ruamel.yaml.clib>=0.1.2; platform_python_implementation == "CPython" and python_version < "3.10" (from ruamel-yaml)
ERROR: No matching distribution found for ruamel.yaml.clib>=0.1.2; platform_python_implementation == "CPython" and python_version < "3.10"

and the provider trick does not work.

[PierreR]

We hit the same issue today as well 😉

[TyberiusPrime]

Appreciate it, this fixes it beautifully.