these 2 derivations will be built:
  /nix/store/dx1h7nw9lj561bp1mpknwcw69mwxh3rq-nixos-test-driver-pg_cron.drv
  /nix/store/cwhl8x1x7y1rya1knzm3y9lq37yj54w2-vm-test-run-pg_cron.drv