W: Failed to fetch http: //ppa.launchpad.net/picaso/octave/ubuntu/dists/trusty/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http: //ppa.launchpad.net/picaso/octave/ubuntu/dists/trusty/main/binary-i386/Packages 404 Not Found
W: Failed to fetch http: //ppa.launchpad.net/kilian/f.lux/ubuntu/dists/trusty/main/binary-amd64/Packages 404 Not Found
W: Failed to fetch http: //ppa.launchpad.net/kilian/f.lux/ubuntu/dists/trusty/main/binary-i386/Packages 404 Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
我无法更新我的 ubuntu 14.04 并且我也遇到了一些 404 未找到的情况。