anchor.diff:  { stdenv, fetchurl, pkgconfig, python3, makeWrapper, pygtk
   , webkit, glib_networking, gsettings_desktop_schemas, pythonPackages
   }:
  +# This package needs python3 during buildtime,
  +# but Python 2 + packages during runtime.
   
   stdenv.mkDerivation rec {
     name = "uzbl-v0.9.0";
  
positive.code:   preConfigure = ''
      makeFlags="$makeFlags PREFIX=$out"
      makeFlags="$makeFlags PYINSTALL_EXTRA=--prefix=$out"
      mkdir -p $out/lib/python3.4/site-packages/
      export PYTHONPATH=$PYTHONPATH:$out/lib/python3.4/site-packages/
    '';
  
    preFixup = ''
  
negative.code: 
    nativeBuildInputs = [ pkgconfig python3 makeWrapper ];
  
    buildInputs = [ gsettings_desktop_schemas webkit ];
    propagatedBuildInputs = [ pygtk pythonPackages.six ];
  }
  