these 2 derivations will be built:
  /nix/store/8lvd5hdass2i3391m2q1zj98331w0gn9-nixos-test-driver-postgis.drv
  /nix/store/3qjcvk3v6y8w0h99syj9i6s9xia4bq5w-vm-test-run-postgis.drv