anchor.diff: -{stdenv, lib, fetchurl, cmake, zlib, libxml2, eigen, python, cairo, pcre, pkg-config, swig, rapidjson }:
  +{ stdenv, lib, fetchFromGitHub, cmake, zlib, libxml2, eigen, python, cairo, pcre, pkg-config, swig, rapidjson }:
   
   stdenv.mkDerivation rec {
     pname = "openbabel";
     version = "3.1.1";
   
  -  src = fetchurl {
  -    url = "https://github.com/openbabel/openbabel/archive/openbabel-${lib.replaceStrings ["."] ["-"] version}.tar.gz";
  -    sha256 = "c97023ac6300d26176c97d4ef39957f06e68848d64f1a04b0b284ccff2744f02";
  +  src = fetchFromGitHub {
  +    owner = "openbabel";
  +    repo = "openbabel";
  +    rev = "openbabel-${lib.replaceStrings ["."] ["-"] version}";
  +    sha256 = "sha256-wQpgdfCyBAoh4pmj9j7wPTlMtraJ62w/EShxi/olVMY=";
     };
  -
   
     buildInputs = [ zlib libxml2 eigen python cairo pcre swig rapidjson ];
   
  
positive.code:         package_data = {'openbabel' : ['_openbabel.so']}
      )
      EOF
      '';
  
    meta = with lib; {
      description = "A toolbox designed to speak the many languages of chemical data";
  
negative.code:     "-DPYTHON_BINDINGS=ON"
    ];
  
    postFixup = ''
      cat <<EOF > $out/lib/python$pythonMajorMinor/site-packages/setup.py
      from distutils.core import setup
  