anchor.diff:  
   let
   
  -  tornado_4_0_1 = pythonPackages.buildPythonPackage rec {
  +  tornado_4_0_2 = pythonPackages.buildPythonPackage rec {
       name = "tornado-${version}";
  -    version = "4.0.1";
  +    version = "4.0.2";
   
       propagatedBuildInputs = with pythonPackages; [ backports_ssl_match_hostname_3_4_0_2 certifi ];
   
       src = fetchurl {
         url = "mirror://pypi/t/tornado/${name}.tar.gz";
  -      sha256 = "00crp5vnasxg7qyjv89qgssb69vd7qr13jfghdryrcbnn9l8c1df";
  +      sha256 = "1yhvn8i05lp3b1953majg48i8pqsyj45h34aiv59hrfvxcj5234h";
       };
     };
   
  
positive.code:     };
  
      # This is needed for compatibility with OctoPrint
      propagatedBuildInputs = [ tornado_4_0_1 ];
  
      meta = with stdenv.lib; {
        description = "SockJS python server implementation on top of Tornado framework";
        homepage = "http://github.com/mrjoes/sockjs-tornado/";
        license = licenses.mit;
        platforms = platforms.all;
        maintainers = with maintainers; [ abbradar ];
      };
    };
  
  in pythonPackages.buildPythonApplication rec {
    name = "OctoPrint-${version}";
    version = "1.2.17";
  
    src = fetchFromGitHub {
      owner = "foosel";
      repo = "OctoPrint";
      rev = version;
      sha256 = "1di2f5npwsfckx5p2fl23bl5zi75i0aksd9qy4sa3zmw672337fh";
    };
  
    # We need old Tornado
    propagatedBuildInputs = with pythonPackages; [
      awesome-slugify flask_assets rsa requests2 pkginfo watchdog
      semantic-version flask_principal werkzeug flaskbabel tornado_4_0_1
      psutil pyserial flask_login netaddr markdown sockjs-tornado
      pylru pyyaml sarge feedparser netifaces
    ];
  
    # Jailbreak dependencies.
  
negative.code:       -e 's,Flask-Principal>=[^"]*,Flask-Principal,g' \
        -e 's,markdown>=[^"]*,markdown,g' \
        -e 's,Flask-Assets>=[^"]*,Flask-Assets,g' \
        -e 's,rsa>=[^"]*,rsa,g' \
        -e 's,PyYAML>=[^"]*,PyYAML,g' \
        -e 's,flask>=[^"]*,flask,g' \
        -e 's,Click>=[^"]*,Click,g' \
        -e 's,websocket-client>=[^"]*,websocket-client,g' \
        -e 's,scandir>=[^"]*,scandir,g' \
        setup.py
    '';
  
  