The mirror of Ubuntu which you are using in an unofficial one and the release upgrader did not fall back to a generic one in your case. If you just want to upgrade please switch to an official mirror of the Ubuntu archive. You can find a list here:
https://launchpad.net/ubuntu/+archivemirrors
The mirror of Ubuntu which you are using in an unofficial one and the release upgrader did not fall back to a generic one in your case. If you just want to upgrade please switch to an official mirror of the Ubuntu archive. You can find a list here:
https:/ /launchpad. net/ubuntu/ +archivemirrors