nixos/system-sysusers: include username in assertion

        message = "config.users.mutableUsers requires config.system.etc.overlay.enable.";

      }

    ] ++ (lib.mapAttrsToList

      (_username: opts: {

      (username: opts: {

        assertion = !opts.isNormalUser;

        message = "systemd-sysusers doesn't create normal users. You can currently only use it to create system users.";

        message = "${username} is a normal user. systemd-sysusers doesn't create normal users, only system users.";

      })

      userCfg.users)

    ++ lib.mapAttrsToList