def check_path_header(req, name, length, error_msg):
    """
    Validate that the value of path-like header is
    well formatted. We assume the caller ensures that
    specific header is present in req.headers.

    :param req: HTTP request object
    :param name: header name
    :param length: length of path segment check
    :param error_msg: error message for client
    :returns: A tuple with path parts according to length
    :raise: HTTPPreconditionFailed if header value
            is not well formatted.
    """
    src_header = unquote(req.headers.get(name))
    if not src_header.startswith('/'):
        src_header = '/' + src_header
    try:
        return utils.split_path(src_header, length, length, True)
    except __HOLE__:
        raise HTTPPreconditionFailed(
            request=req,
            body=error_msg)
dataset/ETHPy150Open openstack/swift/swift/common/constraints.py/check_path_header