maintainers/scripts/check-hydra-by-maintainer: use concatStringsSep

      # trying to only add spaces as necessary for optional args

      # with optStr don't need spaces between nix templating

      optStr = cond: string: lib.optionalString cond "${string} ";

      command = "hydra-check ${optStr short "--short"}${optStr (extra != "") extra}${lib.escapeShellArgs packages}";

      args = [

        "hydra-check"

      ]

      ++ (lib.optional short "--short")

      ++ (lib.optional (extra != "") extra)

      ++ (map lib.escapeShellArg packages);

      command = lib.concatStringsSep " " args;

    in

    ''

      # if user presses ctrl-c during run