Você não tem o cd-rom, por isso não está encontrando. Vá para o software e atualize as configurações e desmarque os CDs que você não possui. Em seguida, ele deve fazer a atualização automaticamente quando você fechar o applet.
Eu tentei atualizar pacotes usando o comando apt-get update , que falhou com a seguinte mensagem de erro:
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/main/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/multiverse/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/restricted/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/universe/binary-amd64/Packages Please use apt-cdrom to make this CD-ROM recognized by APT. apt-get update cannot be used to add new CD-ROMs
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/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
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/multiverse/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
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/restricted/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
W: Failed to fetch cdrom://Kubuntu 15.10 _Wily Werewolf_ - Release amd64 (20151021)/dists/wily/universe/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.[![enter image description here][1]][1]
Você não tem o cd-rom, por isso não está encontrando. Vá para o software e atualize as configurações e desmarque os CDs que você não possui. Em seguida, ele deve fazer a atualização automaticamente quando você fechar o applet.