Try to load metadata from file.

def _load_meta_cache(self):
        """ Try to load metadata from file. """
        try:
            if self._should_invalidate_cache():
                os.remove(self._cache_filename)
            else:
                with open(self._cache_filename, 'rb') as f:
                    self._document_meta = compat.pickle.load(f)
        except (OSError, IOError, compat.pickle.PickleError,
                ImportError, AttributeError):
            pass