Hi! A user for a flake of mine uses macOS. Unfortunately I don't own a Mac, so I have no idea of the nix-darwin ecosystem. They get this error when running an activation script. nixpkgs is the latest nixos-25.11 (but a week old one had the same result):

       last 9 log lines:
       > Running phase: patchPhase
       > Running phase: updateAutotoolsGnuConfigScriptsPhase
       > Running phase: configurePhase
       > no configure script, doing nothing
       > Running phase: buildPhase
       > Traceback (most recent call last):
       >   File "/nix/store/5g45axkqi74cigpqpz3s9yayn80k6dv7-build-config.py", line 4, in <module>
       >     import yaml
       > ModuleNotFoundError: No module named 'yaml'
       For full logs, run:
         nix log /nix/store/rs6nnmijyfhy9p4q1d1iyf2w4a2j9c44-riptide-build-config.drv

nativeBuildInputs & buildPhase:

    nativeBuildInputs = [
      (pkgs.python314.withPackages (python-pkgs: [
        python-pkgs.pyyaml
        python-pkgs.mergedeep
      ]))
    ];

    buildPhase = ''
      runHook preBuild
      python3 \
        $src \
        ${lib.escapeShellArg (builtins.toJSON cfg)} \
        ${hostsFile} \
        ./config.yml
      runHook postBuild
    '';