anchor.diff:  
     darcsver = buildPythonPackage (rec {
       name = "darcsver-1.7.4";
  +    disabled = isPy3k;
   
       src = fetchurl {
         url = "http://pypi.python.org/packages/source/d/darcsver/${name}.tar.gz";
  
positive.code: 
    dulwich = buildPythonPackage rec {
      name = "dulwich-0.8.7";
  
      src = fetchurl {
        url = "http://samba.org/~jelmer/dulwich/${name}.tar.gz";
  
negative.code:   };
  
    netifaces = buildPythonPackage rec {
      version = "0.10.4";
      name = "netifaces-${version}";
  
      src = fetchurl {
        url = "http://pypi.python.org/packages/source/n/netifaces/${name}.tar.gz";
        sha256 = "1plw237a4zib4z8s62g0mrs8gm3kjfrp5sxh6bbk9nl3rdls2mln";
      };
  
      meta = {
  