Split the path up into useful parts: bucket, obj_key

def _parse_url(url=None):
    """Split the path up into useful parts: bucket, obj_key"""
    if url is None:
        return ('', '')

    scheme, netloc, path, _, _ = parse.urlsplit(url)

    if scheme != 's3':
        raise InvalidURL(url, "URL scheme must be s3://")

    if path and not netloc:
        raise InvalidURL(url)

    return netloc, path[1:]