error:
       … in the right operand of the update (//) operator
         at /var/lib/nixbot/worktrees/1042-1fbfadbba995-94b7b6da/nix/checks/default.nix:57:4:
           56| }
           57| // lib.optionalAttrs (lib.hasSuffix "linux" system) {
             |    ^
           58|   nixos-test-niks3 = pkgs.callPackage ./nixos-test-niks3.nix {

       … while evaluating the attribute 'legacyPackages.x86_64-darwin'
         at «github:NixOS/nixpkgs/9ab0784f4b4b98a4f100d4cb2245d791cdccf70a?narHash=sha256-ajlPoJbp28hK8Zgua3n%2Bg4LuzGVGlKfs94jA2VVUa3Q%3D»/lib/attrsets.nix:987:47:
          986|   */
          987|   nameValuePair = name: value: { inherit name value; };
             |                                               ^
          988|

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: Nixpkgs 26.11 has dropped support for x86_64-darwin.

       The 26.05 stable branch still supports x86_64-darwin, and will
       receive security fixes until the end of 2026. If you use channels,
       you can switch to 26.05 as follows:

           $ sudo nix-channel --add https://nixos.org/channels/nixpkgs-26.05-darwin nixpkgs
           $ sudo nix-channel --update

       If this doesn’t work, you may need to run:

           # Lack of sudo is deliberate:
           $ nix-channel --remove nixpkgs

       If you use flakes, switch your flake input:

           inputs.nixpkgs = {
             url = "github:NixOS/nixpkgs/nixpkgs-26.05-darwin";
           };

       See the release notes for more information and alternatives:

         https://nixos.org/manual/nixpkgs/unstable/release-notes#x86_64-darwin-26.11