运行时：
sudo apt-get update && sudo apt-get dist-upgrade
我得到了这个输出：
Ign http://security.ubuntu.com utopic-security InRelease
Ign http://gb.archive.ubuntu.com utopic InRelease
Ign http://extras.ubuntu.com utopic InRelease
Get:1 http://security.ubuntu.com utopic-security Release.gpg [933 B]
Ign http://dl.google.com stable InRelease
Ign http://gb.archive.ubuntu.com utopic-updates InRelease
Get:2 http://extras.ubuntu.com utopic Release.gpg [72 B]
Get:3 http://security.ubuntu.com utopic-security Release [62.0 kB]
Ign http://gb.archive.ubuntu.com utopic-backports InRelease
Get:4 http://dl.google.com stable Release.gpg [198 B]
Hit http://extras.ubuntu.com utopic Release
Hit http://gb.archive.ubuntu.com utopic Release.gpg
Get:5 http://dl.google.com stable Release [1,347 B]
Err http://dl.google.com stable Release
Get:6 http://gb.archive.ubuntu.com utopic-updates Release.gpg [933 …