anchor.diff:  
     propagatedBuildInputs = [
       serpent
  -  ] ++ lib.optionals (isPy27 || isPy33) [ selectors34 ];
  +  ] ++ lib.optionals isPy27 [ selectors34 ];
   
     buildInputs = [
       dill
  
positive.code:     msgpack
    ];
  
    checkPhase = ''
      ${python.interpreter} setup.py test
    '';
  
    meta = with stdenv.lib; {
  
negative.code: , cloudpickle
  , msgpack
  , isPy27
  , selectors34
  , pytest
  }:
  
  buildPythonPackage rec {
  