anchor.diff:      sha256 = "83657d894c90d5681d62155c82bda9c1187827525880eda8ff5df4ec813437c3";
     };
   
  -  buildInputs = [ unittest2 ];
  -  propagatedBuildInputs = [ funcsigs six pbr ];
  +  propagatedBuildInputs = [ six pbr ] ++ lib.optionals isPy27 [ funcsigs ];
   
     # On PyPy for Python 2.7 in particular, Mock's tests have a known failure.
     # Mock upstream has a decoration to disable the failing test and make
  
positive.code: { stdenv
  , buildPythonPackage
  , fetchPypi
  , unittest2
  , funcsigs
  , six
  , pbr
  
negative.code:     ${python.interpreter} -m unittest discover
    '';
  
    meta = with lib; {
      description = "Mock objects for Python";
      homepage = http://python-mock.sourceforge.net/;
      license = licenses.bsd2;
    };
  
  }
  