these 3 derivations will be built:
  /nix/store/fyf72smjm8rlnsg6asbsmlf9krnl7s4n-docker-image-sources.drv
  /nix/store/4v20x2i3x5s94j1cdq9qj55zxvwvy8i9-docker-image-inputs.drv
  /nix/store/kkh47v24zb71xy71bbc75y44y1f5x1xs-docker-image-inputs-hash.drv