these 2 derivations will be built:
  /nix/store/nf0zxiihn46m0b45si3r29gda9wz50ji-nixos-test-driver-pgtap.drv
  /nix/store/ks9mb9m4z5wj1flzcak893fl8v3d0jny-vm-test-run-pgtap.drv