anchor.diff:    # xandikos and radicale is only a optional test dependency, not available for python3
     postPatch = ''
       substituteInPlace setup.py \
  -      --replace ", 'xandikos'" "" \
  +      --replace ", 'xandikos<0.2.4'" "" \
         --replace ", 'radicale'" ""
     '';
   
  
positive.code:     description = "This project is a CalDAV (RFC4791) client library for Python.";
      homepage = "https://github.com/python-caldav/caldav";
      license = licenses.asl20;
      maintainers = with maintainers; [ marenz ];
      #broken = true; # requires radicale which is not packaged yet
    };
  }
  
negative.code: 
  buildPythonPackage rec {
    pname = "caldav";
    version = "0.8.2";
  
    src = fetchFromGitHub {
      owner = "python-caldav";
      repo = pname;
      rev = "v${version}";
      hash = "sha256-2mpE1aLipps4X/3EF0oKHXDcrgUh78/fxY6y1B1V2IU=";
    };
  
    propagatedBuildInputs = [
      vobject
      lxml
      requests
      six
    ];
  
    checkInputs = [
      icalendar
      nose
      tzlocal
      pytz
    ];
  
    checkPhase = ''
  