these 2 derivations will be built:
  /nix/store/qp25kpmq1l16489fad7njax2plgzccvl-nixos-test-driver-pg_cron.drv
  /nix/store/khc2zfjh7rdysl5jnqgh537dppcp7dba-vm-test-run-pg_cron.drv