these 4 derivations will be built:
  /nix/store/7cy0i30wy58r3y4nn7pq0h8argljrqam-run-nixos-vm.drv
  /nix/store/bdcgmfrx4rvbcxhsh693yd2iz06v5nnp-nixos-vm.drv
  /nix/store/0sh0qh6wpxs674n6bg8xlb5gx29xddbg-nixos-test-driver-postgis.drv
  /nix/store/26c1j2nswqqi2f55pq60hzdw0kpbmsjy-vm-test-run-postgis.drv