anchor.diff: -{ stdenv
  +{ lib
   , buildPythonPackage
  -, fetchdarcs
  +, fetchFromGitHub
   , isPy3k
   , pkgs
   , cython
  
positive.code:   buildInputs = with pkgs; [ alsaLib ffmpeg libv4l sqlite libvpx ];
    propagatedBuildInputs = [ cython pkgs.openssl dnspython dateutil xcaplib msrplib lxml python-otr ];
  
    meta = with stdenv.lib; {
      description = "SIP SIMPLE implementation for Python";
      homepage = http://sipsimpleclient.org/;
      license = licenses.gpl3;
  
negative.code: 
  buildPythonPackage rec {
    pname = "sipsimple";
    version = "3.4.2";
    disabled = isPy3k;
  
    src = fetchFromGitHub {
      owner = "AGProjects";
      repo = "python-sipsimple";
      rev = "release-${version}";
      sha256 = "094xf343d6zjhg9jwbm3dr74zq264cyqnn22byvm2m88lnagmhmr";
    };
  
    preConfigure = ''
  