anchor.diff:  , fetchurl
   , fetchFromGitHub
   , lib
  -, python2Packages
  +, python3Packages
   }:
   
   # TODO: build release tarballs, repo vendors pdfs
  
positive.code:   name = "opengl-headers-${version}";
  
    src = fetchurl {
      url = "http://opengl-headers.tar.xz";  # dummy url
      multihash = "QmZdRTzsSxGWTSzmChywUgo6drKFoho8qDh4FagumAM3eS";
      sha256 = "7cfa0ed4091b4d04c33b1be3c30361f9613b7301744f0b4b6397b923d82295d0";
    };
  
negative.code:       };
  
        nativeBuildInputs = [
          python3Packages.lxml
          python3Packages.python
        ];
  
        postPatch = ''
  