error:
       … while evaluating the attribute 'drvPath'
         at «github:NixOS/nixpkgs/643809054d65fdd466a63e3155b8c498cb483c04?narHash=sha256-vUfIeBEfpbAfZ5zjgIkYk7eHBeVfCYVjLbWnMkseYnk%3D»/lib/customisation.nix:415:11:
          414|         // {
          415|           drvPath =
             |           ^
          416|             assert condition;

       … while calling the 'derivationStrict' builtin
         at «nix-internal»/derivation-internal.nix:37:12:
           36|
           37|   strict = derivationStrict drvAttrs;
             |            ^
           38|

       … while evaluating the option `driverConfigurationFile':

       … while evaluating the option `driverConfiguration.containers.server.start_script':

       … while evaluating definitions from `/nix/store/2a2yjwdqfc0hrfhjpx5fny4fl5fmdgbx-source/nixos/lib/testing/driver-configuration.nix':

       … while evaluating definitions from `/nix/store/2a2yjwdqfc0hrfhjpx5fny4fl5fmdgbx-source/nixos/modules/virtualisation/nspawn-container':

       … while evaluating the option `containers.server.system.build.toplevel':

       … while evaluating definitions from `/nix/store/2a2yjwdqfc0hrfhjpx5fny4fl5fmdgbx-source/nixos/modules/system/activation/top-level.nix':

       … while evaluating the option `containers.server.services.nginx.virtualHosts."acme.test".locations."~ ^/(assets|img)".root':

       … while evaluating definitions from `/nix/store/2a2yjwdqfc0hrfhjpx5fny4fl5fmdgbx-source/nixos/modules/services/web-apps/mobilizon.nix':

       … while evaluating the option `containers.server.services.mobilizon.package':

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

       error: undefined variable 'cacert'
       at «git+file:///var/lib/nixbot/worktrees/13-07524b31762c-83?ref=HEAD&rev=3b3a91fab6c7a4ffcde192a609e7a923733f3f5b»/default.nix:56:63:
           55|           postInstall = old.postInstall or "" + ''
           56|             find . -type f -name cacerts.pem -exec ln -sfn '${cacert}/etc/ssl/certs/ca-bundle.crt' {} \;
             |                                                               ^
           57|           '';