these 2 derivations will be built:
  /nix/store/8z5zs29llk0flaa59kyxch4r863swcxd-nixos-test-driver-pg_cron.drv
  /nix/store/cc8ib1n35zndafjmfk6cdrwjnpi0xkx5-vm-test-run-pg_cron.drv