these 3 derivations will be built:
  /nix/store/d6m588rjwzp68bkwj7b54gsjkqdqng71-source.drv
  /nix/store/7wc5bva0xjzpqsh48lhxbmjpaivhbp02-iets-deps-0.1.0.drv
  /nix/store/y5zbqr9s68pqxv7hqbi65yksr1y8ny0h-iets-doctest-0.1.0.drv