Installing dream2nix package in docker container

[chrichrichri]

Hi everybody,

maybe it is a stupid questions, but I was not able to get it running. I am trying to install a python-package which I packaged using dream2nix (Packaged just like in the example ) within a docker container. The docker image is created like below.

  base_image = import ("${nix}/docker.nix") {
      inherit pkgs;
      name = "nix-ci-base";
      maxLayers = 10;
      extraPkgs = with pkgs; [
        <my_dream2nix_python_package_repo_name>.packages.${pkgs.system}.<package_to_install>
      ];
      # change this is you want
      channelURL = "https://nixos.org/channels/nixpkgs-24.05";
      # allow using the new flake commands in our workflows
      experimental-features = ["nix-command" "flakes"];
      };
  };

Building always fails with:

at /nix/store/pk6hi49dmdbspimwxr64abvc0frz2wjr-source/docker.nix:180:25:

    outPath = "${drv}";
    system = "${drv.system}";
                         ^
    type = "derivation";

error: attribute 'system' missing

Does anyone have the idea how to resolve this problem? When Installing outside of a docker container, everything works perfectly.

Thanks