Is the system indexing?
        Return True if so, False if not.

def db_is_indexing(cls, impl, working_dir):
        """
        Is the system indexing?
        Return True if so, False if not.
        """
        indexing_lockfile_path = config.get_lockfile_filename(impl, working_dir)
        return os.path.exists(indexing_lockfile_path)