these 2 derivations will be built:
  /nix/store/4y4y6y1ym4q3j12832x3g6574m17jn7x-nixos-test-driver-pgtap.drv
  /nix/store/j4mx99s8gnr624j0xc2kc4bhkn9hhhfb-vm-test-run-pgtap.drv