these 2 derivations will be built:
  /nix/store/hbp006dkszj883wg5nmy3vspk2vj2pir-nixos-test-driver-pg_cron.drv
  /nix/store/8if7pnjxxk2cf9nazmxfpkvnp9qznymb-vm-test-run-pg_cron.drv