failed to download repository information

[jose]

W:The repository 'cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release i386 (20160420.1) xenial Release' does not have a Release file., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., W:GPG error: http://ppa.launchpad.net/paul-climbing/ppa/ubuntu xenial InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8C851674F96FD737, W:The repository 'http://ppa.launchpad.net/paul-climbing/ppa/ubuntu xenial InRelease' is not signed., W:Data from such a repository can't be authenticated and is therefore potentially dangerous to use., W:See apt-secure(8) manpage for repository creation and user configuration details., E:Failed to fetch cdrom://Ubuntu 16.04 LTS _Xenial Xerus_ - Release i386 (20160420.1)/dists/xenial/main/binary-i386/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs, E:Some index files failed to download. They have been ignored, or old ones used instead.