def _clean_key(root_key, filekey):
    """Return the cleaned key 'filekey', using 'root_key' as the root

      Args:
            root_key (str): root_key for accessing object store
            filekey (str): filename to access in object store
        Returns:
            str: Location to access the file

    """
    if root_key:
        return "%s/%s" % (str(root_key), str(filekey))
    else:
        return str(filekey)