Err http://ppa.launchpad.net utopic/main amd64 Packages
404 Not Found
Get:63 http://in.archive.ubuntu.com utopic/universe Sources [6,736 kB]
Err http://ppa.launchpad.net utopic/main i386 Packages
404 Not Found
W: Failed to fetch http://ppa.launchpad.net/cdemu/ppa/ubuntu/dists/utopic/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http://ppa.launchpad.net/cdemu/ppa/ubuntu/dists/utopic/main/binary-i386/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
这种情况怎么办？？