these 2 derivations will be built:
  /nix/store/0ry7n9ldskwh5y3kmjp3fkrhqbs88m5d-nixos-test-driver-pg_cron.drv
  /nix/store/xlzrk3rkird6hl3a2ssw31dv568w58cy-vm-test-run-pg_cron.drv