anchor.diff:  
   
     # TODO
  -  # py.error.EACCES: [Permission denied]: mkdir('/homeless-shelter',)
  -  # builder for `/nix/store/0czwg0n3pfkmpjphqv1jxfjlgkbziwsx-python-tox-1.4.3.drv' failed with exit code 1
  +  # Installs correctly but fails tests that involve simple things like:
  +  # cmd.run("tox", "-h")
  +  # also, buildPythonPackage needs to supply the tox.ini correctly for projects that use tox for their tests
  +  #
     # tox = buildPythonPackage rec {
  -  #   name = "tox-1.4.3";
  +  #   name = "tox-1.7.0";
     #
  -  #   buildInputs = [ py virtualenv ];
  +  #   propagatedBuildInputs = [ py virtualenv ];
     #
     #   src = fetchurl {
  -  #     url = "https://pypi.python.org/packages/source/t/tox/tox-1.4.3.tar.gz";
  -  #     md5 = "3727d5b0600d92edf2229a7ce6a0f752";
  +  #     url = "https://pypi.python.org/packages/source/t/tox/${name}.tar.gz";
  +  #     md5 = "5314ceca2b179ad4a9c79f4d817b8a99";
     #   };
     # };
   
  
positive.code:       md5 = "90a82400074b50a9e73c3045ed9ac217";
      };
  
      buildInputs = [ virtualenv virtualenv-clone ];
  
      meta = with stdenv.lib; {
        description = "Tools to manage multiple virtualenvs written in pure python, a virtualenvwrapper rewrite";
  
negative.code: 
  
    py = buildPythonPackage rec {
      name = "py-1.4.20";
  
      src = fetchurl {
        url = "https://pypi.python.org/packages/source/p/py/${name}.tar.gz";
        md5 = "5f1708be5482f3ff6711dfd6cafd45e0";
      };
    };
  
  