anchor.diff:  { stdenv
   , lib
   , buildPythonPackage
  +, pythonOlder
   , fetchFromGitHub
   , six
  -, enum34
   , decorator
   , nose
   , krb5Full
   , darwin
  -, isPy27
   , parameterized
   , shouldbe
   , cython
  
positive.code:   propagatedBuildInputs =  [
      decorator
      six
    ] ++ lib.optional isPy27 enum34;
  
    buildInputs = lib.optionals stdenv.isDarwin [
      darwin.apple_sdk.frameworks.GSS
  
negative.code: 
  buildPythonPackage rec {
    pname = "gssapi";
    version = "1.6.9";
    disabled = pythonOlder "3.6";
  
    src = fetchFromGitHub {
      owner = "pythongssapi";
      repo = "python-${pname}";
      rev = "v${version}";
      sha256 = "1shm3pc0l2r91qadkpq4bx45my0165nw3kdcp0gw4lk50z215hag";
    };
  
    # It's used to locate headers
  