these 2 derivations will be built:
  /nix/store/i4z1r7mb1adca2c2bv4xq35pfh0k424a-mardi-gras-0.34.0.drv
  /nix/store/d9g227ginrlh8zfbhxqcxx9khhy5m3yc-check-mardi-gras.drv