these 2 derivations will be built:
  /nix/store/c3x9lg2sh2khfnqxlqvqvk6lzc875l8g-nixos-test-driver-postgis.drv
  /nix/store/9vcl4sxcn0nlkyw0aq29bj4ng5wv6gkb-vm-test-run-postgis.drv