Continuo recebendo a mensagem antiga que experimentei de atualizações anteriores de lá.
Alterar o servidor e atualizar parece não funcionar mais.
W:There is no public key available for the following key IDs: 1397BC53640DB551
W:Failed to fetch htt p://extras.ubuntu.com/ubuntu/dists/vivid/main/source/Sources 404 Not Found [IP: 91.189.92.152 80]
W:Failed to fetch htt p://extras.ubuntu.com/ubuntu/dists/vivid/main/binary-amd64/Packages 404 Not Found [IP: 91.189.92.152 80]
W:Failed to fetch htt p://extras.ubuntu.com/ubuntu/dists/vivid/main/binary-i386/Packages 404 Not Found [IP: 91.189.92.152 80]
E:Some index files failed to download. They have been ignored, or old ones used instead.