anchor.diff:  { lib
   , buildPythonPackage
  +, isPy27
   , fetchPypi
   , glibcLocales
   , pytest
  
positive.code: buildPythonPackage rec {
    pname = "traitlets";
    version = "5.0.5";
  
    src = fetchPypi {
      inherit pname version;
  
negative.code:     LC_ALL="en_US.UTF-8" py.test
    '';
  
    meta = {
      description = "Traitlets Python config system";
      homepage = "http://ipython.org/";
  