Объясните как устранить ошибку при обновлении.

ERROR###ERROR###ERROR###ERROR###ERROR###ERROR###ERROR
W:Failed to fetch http://ppa.launchpad.net/upubuntu-com/graphics/ubuntu/dists/raring/main/source/Sources 404 Not Found
, W:Failed to fetch http://ppa.launchpad.net/upubuntu-com/graphics/ubuntu/dists/raring/main/binary-amd64/Packages 404 Not Found
, W:Failed to fetch http://ppa.launchpad.net/upubuntu-com/graphics/ubuntu/dists/raring/main/binary-i386/Packages 404 Not Found
, E:Some index files failed to download. They have been ignored, or old ones used instead.