these 2 derivations will be built:
  /nix/store/jv7ba63wqkmyzx0y8r0qmy8f4y5n281w-nixos-test-driver-pg_cron.drv
  /nix/store/rkkz86kjhq350jiyran4f2xvcw1jv3bg-vm-test-run-pg_cron.drv