anchor.diff:        werkzeug
         itsdangerous
         dateutil
  -      futures
         requests2
         six
         pygments
  
positive.code: 
    bokeh = buildPythonPackage rec {
      name = "bokeh-${version}";
      version = "0.12.1";
  
      src = pkgs.fetchurl {
        url = "mirror://pypi/b/bokeh/${name}.tar.gz";
        sha256 = "06d3ed14308f550376d5b0c7e9f2bacb3ff5bbcceefd7f6369d070de71dfa563";
      };
  
      disabled = isPyPy;
  
negative.code:       tornado
        colorama
        ]
        ++ optionals ( !isPy3k ) [ futures ]
        ++ optionals ( isPy26 ) [ argparse ]
        ++ optionals ( !isPy3k && !isPyPy ) [ websocket_client ]
        ++ optionals ( !isPyPy ) [ numpy pandas greenlet ];
  