def _get_path_specific_lower(self):
        """Return a copy of self._path_specific with the paths lower-cased."""
        if self._path_specific_lower is None:
            self._path_specific_lower = []
            for (sub_paths, path_rules) in self._path_specific:
                sub_paths = map(str.lower, sub_paths)
                self._path_specific_lower.append((sub_paths, path_rules))
        return self._path_specific_lower