anchor.diff:  
     flexget = buildPythonPackage rec {
       name = "FlexGet-1.2.161";
  +    disabled = isPy3k;
   
       src = fetchurl {
         url = "https://pypi.python.org/packages/source/F/FlexGet/${name}.tar.gz";
  
positive.code: 
    pika = buildPythonPackage {
      name = "pika-0.9.12";
      src = fetchurl {
        url = https://pypi.python.org/packages/source/p/pika/pika-0.9.12.tar.gz;
        md5 = "7174fc7cc5570314fa3cfaa729106482";
  
negative.code: 
  
    paste_deploy = buildPythonPackage rec {
      version = "1.5.2";
      name = "paste-deploy-${version}";
  
      src = fetchurl {
        url = "http://pypi.python.org/packages/source/P/PasteDeploy/PasteDeploy-${version}.tar.gz";
        md5 = "352b7205c78c8de4987578d19431af3b";
      };
  
      buildInputs = [ nose ];
  