anchor.diff:      };
     };
   
  +  msgpack = buildPythonPackage rec {
  +    name = "msgpack-python-${version}";
  +    version = "0.4.2";
  +
  +    src = pkgs.fetchurl {
  +      url = "https://pypi.python.org/packages/source/m/msgpack-python/${name}.tar.gz";
  +      md5 = "e3a0fdfd864c72c958bb501d39b39caf";
  +    };
  +
  +    propagatedBuildInputs = with self; [ ];
  +  };
   
     msrplib = buildPythonPackage rec {
       name = "python-msrplib-${version}";
  
positive.code: 
  
    requests2 = buildPythonPackage rec {
      name = "requests-2.2.1";
  
      src = pkgs.fetchurl {
        url = "http://pypi.python.org/packages/source/r/requests/${name}.tar.gz";
        md5 = "ac27081135f58d1a43e4fb38258d6f4e";
      };
  
      meta = {
  
negative.code:     };
    };
  
    locustio = buildPythonPackage rec {
      name = "locustio-0.7.2";
  
      src = pkgs.fetchurl {
        url = "https://pypi.python.org/packages/source/l/locustio/${name}.tar.gz";
        md5 = "90cf4d029d58ad58d19ea17a16e59c34";
      };
  
      propagatedBuildInputs = [ self.msgpack self.requests2 self.flask self.gevent self.pyzmq ];
      buildInputs = [ self.mock self.unittest2 ];
  
      meta = {
        homepage = http://locust.io/;
        description = "A load testing tool";
      };
    };
  
    lockfile = buildPythonPackage rec {
      name = "lockfile-0.9.1";
  