these 3 derivations will be built:
  /nix/store/nz2k8g142d0d235z7nxz61f5j7gldx87-cpa-usage-keeper-frontend-1.15.8.drv
  /nix/store/w03l41iqs5gq7igcwh8qmygsvvi02bmn-cpa-usage-keeper-1.15.8.drv
  /nix/store/h0r311nfah8r621gjb6pvv24vwp99vg7-check-cpa-usage-keeper.drv