W:GPG error: http://download.opensuse.org  Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 977C43A8BA684223,
  W:Failed to fetch http://ppa.launchpad.net/u2t/bleedingedge/ubuntu/dists/trusty/main/source/Sources  404  Not Found
  W:Failed to fetch http://ppa.launchpad.net/u2t/bleedingedge/ubuntu/dists/trusty/main/binary-amd64/Packages  404  Not Found
  W:Failed to fetch http://ppa.launchpad.net/u2t/bleedingedge/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.