anchor.diff:      semantic-version flask_principal werkzeug flaskbabel tornado
       psutil pyserial flask_login netaddr markdown sockjs-tornado
       pylru pyyaml sarge feedparser netifaces click websocket_client
  -    scandir chainmap future
  +    scandir chainmap future dateutil
     ];
   
     buildInputs = with pythonPackages; [ nose mock ddt ];
  
positive.code:       -e 's,werkzeug>=[^"]*,werkzeug,g' \
        -e 's,psutil>=[^"]*,psutil,g' \
        -e 's,requests>=[^"]*,requests,g' \
        setup.py
    '';
  
  
negative.code: 
  in pythonPackages.buildPythonApplication rec {
    name = "OctoPrint-${version}";
    version = "1.3.4";
  
    src = fetchFromGitHub {
      owner = "foosel";
      repo = "OctoPrint";
      rev = version;
      sha256 = "06l8khbq3waaaa4cqpv6056w1ziylkfgzlb28v30i1h234rlkknq";
    };
  
    # We need old Tornado
  