this derivation will be built:
  /nix/store/0zk1grlir3d0qzz81y6nj2rcrqjaijwc-treefmt-check.drv
building '/nix/store/0zk1grlir3d0qzz81y6nj2rcrqjaijwc-treefmt-check.drv'
treefmt-check> treefmt v2.5.0traversed 480 files
treefmt-check> emitted 329 files for processing
treefmt-check> formatted 329 files (1 changed) in 760ms
treefmt-check>  M modules/nixos/hermes/guest.nix
treefmt-check> diff --git a/modules/nixos/hermes/guest.nix b/modules/nixos/hermes/guest.nix
treefmt-check> index 0104e67..353047e 100644
treefmt-check> --- a/modules/nixos/hermes/guest.nix
treefmt-check> +++ b/modules/nixos/hermes/guest.nix
treefmt-check> @@ -52,9 +52,7 @@ let
treefmt-check>    # not operator-wins. `lib.recursiveUpdate` replaces lists, so an
treefmt-check>    # operator list would otherwise drop the built-in skills.
treefmt-check>    guestSettings = lib.recursiveUpdate cfg.settings {
treefmt-check> -    skills.external_dirs = lib.unique (
treefmt-check> -      [ guestSkills ] ++ (cfg.settings.skills.external_dirs or [ ])
treefmt-check> -    );
treefmt-check> +    skills.external_dirs = lib.unique ([ guestSkills ] ++ (cfg.settings.skills.external_dirs or [ ]));
treefmt-check>    };
treefmt-check>  
treefmt-check>    baseGuestPackages =
error: Cannot build '/nix/store/0zk1grlir3d0qzz81y6nj2rcrqjaijwc-treefmt-check.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/vwrcd2v282ghnha9c3qkash3sc9sd7ij-treefmt-check
       Last 19 log lines:
       > treefmt v2.5.0traversed 480 files
       > emitted 329 files for processing
       > formatted 329 files (1 changed) in 760ms
       >  M modules/nixos/hermes/guest.nix
       > diff --git a/modules/nixos/hermes/guest.nix b/modules/nixos/hermes/guest.nix
       > index 0104e67..353047e 100644
       > --- a/modules/nixos/hermes/guest.nix
       > +++ b/modules/nixos/hermes/guest.nix
       > @@ -52,9 +52,7 @@ let
       >    # not operator-wins. `lib.recursiveUpdate` replaces lists, so an
       >    # operator list would otherwise drop the built-in skills.
       >    guestSettings = lib.recursiveUpdate cfg.settings {
       > -    skills.external_dirs = lib.unique (
       > -      [ guestSkills ] ++ (cfg.settings.skills.external_dirs or [ ])
       > -    );
       > +    skills.external_dirs = lib.unique ([ guestSkills ] ++ (cfg.settings.skills.external_dirs or [ ]));
       >    };
       >  
       >    baseGuestPackages =
       For full logs, run:
         nix log /nix/store/0zk1grlir3d0qzz81y6nj2rcrqjaijwc-treefmt-check.drv