def _get_archive_key(whereis):
    """trying to decode the various flavors of whereis info for archives"""
    if whereis.startswith(u'dl+archive:'):
        whereis = whereis[11:]
        if u'tar#path' in whereis or 'zip#path' in whereis:
            return whereis.split('#')[0]
        elif u'.zip/' in whereis:
            return whereis.split('/')[0]
