docs: def _url_chunk_join(self, *args):
          """Join the arguments together to form a predictable URL chunk."""
          # Strip slashes from either side of each path piece.
          pathlets = map(lambda s: s.strip('/'), args)
          # Remove empty pieces.
          pathlets = filter(None, pathlets)
          url = '/'.join(pathlets)
          # If this is a directory, add a trailing slash.
          if args[-1].endswith('/'):
              url = '%s/' % url
          return url