zebux@zebux:~$ LC_ALL=C sudo apt update && sudo apt upgrade
Ign:1 http://fr.archive.ubuntu.com/ubuntu trusty InRelease
Ign:2 http://extras.ubuntu.com/ubuntu trusty InRelease              
Ign:3 http://archive.canonical.com/ubuntu trusty InRelease          
Hit:4 http://security.ubuntu.com/ubuntu trusty-security InRelease   
Hit:5 http://fr.archive.ubuntu.com/ubuntu trusty-updates InRelease  
Hit:6 http://fr.archive.ubuntu.com/ubuntu trusty-backports InRelease
Hit:7 http://archive.canonical.com/ubuntu trusty Release            
Hit:8 http://extras.ubuntu.com/ubuntu trusty Release                
Hit:9 http://fr.archive.ubuntu.com/ubuntu trusty Release                 
Get:10 http://extras.ubuntu.com/ubuntu trusty Release.gpg [72 B]         
Hit:11 https://apt.dockerproject.org/repo ubuntu-xenial InRelease
Ign:10 http://extras.ubuntu.com/ubuntu trusty Release.gpg
Reading package lists... Done   
W: GPG error: http://extras.ubuntu.com/ubuntu trusty Release: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 16126D3A3E5C1192
E: The repository 'http://extras.ubuntu.com/ubuntu trusty Release' is not signed.
N: Updating from such a repository can't be done securely, and is therefore disabled by default.
N: See apt-secure(8) manpage for repository creation and user configuration details.