these 2 derivations will be built:
  /nix/store/40vsyigfn216z7ksax77shwq4cxsd8hq-nixos-test-driver-pg_cron.drv
  /nix/store/ad3m59pwqkyn5q275jb967mym8slzp9h-vm-test-run-pg_cron.drv