anchor.diff:      };
   
       buildInputs = [ pkgs.libev ];
  -    propagatedBuildInputs = [ greenlet ];
  +    propagatedBuildInputs = optionals (!isPyPy) [ greenlet ];
   
       meta = with stdenv.lib; {
         description = "Coroutine-based networking library";
  
positive.code: 
    gevent = buildPythonPackage rec {
      name = "gevent-1.0.1";
      disabled = isPy3k;
  
      src = fetchurl {
        url = "https://pypi.python.org/packages/source/g/gevent/${name}.tar.gz";
  
negative.code: 
    pyuv = buildPythonPackage rec {
      name = "pyuv-0.11.5";
      disabled = isPyPy;  # see https://github.com/saghul/pyuv/issues/49
  
      src = fetchurl {
        url = "https://github.com/saghul/pyuv/archive/${name}.tar.gz";
  