我的do-release-upgrade失败。我收到以下错误消息：
Checking for a new Ubuntu release
Your Ubuntu release is not supported anymore.
For upgrade information, please visit:
http://www.ubuntu.com/releaseendoflife
Err Upgrade tool signature
404 Not Found [IP: 2001:67c:1360:8c01::19 80]
Err Upgrade tool
404 Not Found [IP: 2001:67c:1360:8c01::19 80]
Fetched 0 B in 0s (0 B/s)
WARNING:root:file 'raring.tar.gz.gpg' missing
Failed to fetch
Fetching the upgrade failed. There may be a network problem.
所以它说我的版本不再受支持。我有 Ubuntu Quantal (12.10)。我现在该怎么办？