{
  perSystem =
    { pkgs, lib, ... }:
    {
      # a script that executes all other checks
      packages.impure-checks = pkgs.writeShellScriptBin "impure-checks" ''
        #!${pkgs.bash}/bin/bash
        set -euo pipefail

        unset CLAN_DIR

        export PATH="${
          lib.makeBinPath [
            pkgs.gitMinimal
            pkgs.nix
            pkgs.rsync # needed to have rsync installed on the dummy ssh server
          ]
        }"
        ROOT=$(git rev-parse --show-toplevel)
        cd "$ROOT/pkgs/clan-cli"
        nix develop "$ROOT#clan-cli" -c bash -c "TMPDIR=/tmp python -m pytest -s -m impure ./tests $@"
      '';
    };
}