anchor.diff:  }:
   
   let
  -  sitePackages = "\${out}/lib/${python.libPrefix}/site-packages";
  +  version = "2.9.4";
  +
  +  tarballUrls = version: [
  +    "http://xmlsoft.org/sources/libxml2-${version}.tar.gz"
  +  ];
   in
  -
   stdenv.mkDerivation rec {
     name = "libxml2-${version}";
  -  version = "2.9.3";
   
     src = fetchurl {
  -    url = "http://xmlsoft.org/sources/${name}.tar.gz";
  -    sha256 = "0bd17g6znn2r98gzpjppsqjg33iraky4px923j3k8kdl8qgy7sad";
  +    urls = tarballUrls version;
  +    allowHashOutput = false;
  +    sha256 = "ffb911191e509b966deb55de705387f14156e1a56b21824357cdf0053233633c";
     };
   
     buildInputs = [
  
positive.code:     "--with-lzma=${xz}"
    ];
  
    meta = with stdenv.lib; {
      homepage = http://xmlsoft.org/;
      description = "An XML parsing library for C";
  
negative.code:       wkennington
      ];
      platforms = with platforms;
        x86_64-linux;
    };
  }
  