anchor.diff:    pybrowserid = buildPythonPackage rec {
       name = "PyBrowserID-${version}";
       version = "0.9.2";
  +    disabled = isPy3k; # Errors in the test suite.
  +
       src = pkgs.fetchgit {
         url = https://github.com/mozilla/PyBrowserID.git;
         rev = "refs/tags/${version}";
  
positive.code:     };
    };
  
    configparser = buildPythonPackage rec {
      name = "configparser-${version}";
      version = "3.3.0r2";
  
  
negative.code:   umemcache = buildPythonPackage rec {
      name = "umemcache-${version}";
      version = "1.6.3";
      disabled = isPy3k;
  
      src = pkgs.fetchurl {
        url = "https://pypi.python.org/packages/source/u/umemcache/${name}.zip";
  