these 2 derivations will be built:
  /nix/store/gkah4jl3m8l6q1p3nly2l9ygqj9iqgpn-nixos-test-driver-postgis.drv
  /nix/store/xihfn7grsc6x0vpfnyyd5rck7zf73r01-vm-test-run-postgis.drv