sudo apt update; sudo apt full-upgrade
Hit:1 http://security.ubuntu.com/ubuntu xenial-security InRelease
Hit:3 http://de2.archive.ubuntu.com/ubuntu xenial InRelease
Hit:4 http://de2.archive.ubuntu.com/ubuntu xenial-updates InRelease
Hit:5 http://de2.archive.ubuntu.com/ubuntu xenial-backports InRelease
Hit:2 https://dl.secondarymetabolites.org/repos/deb jessie InRelease      
Ign:6 http://desktop-download.mendeley.com/download/apt stable InRelease  
Hit:7 http://desktop-download.mendeley.com/download/apt stable Release
Hit:9 https://packagecloud.io/slacktechnologies/slack/debian jessie InRelease
Reading package lists... Done
Building dependency tree       
Reading state information... Done
All packages are up to date.
W: http://dl.secondarymetabolites.org/repos/deb/dists/jessie/InRelease: Signature by key BAE5FDAD4B32451E9CF61EAEC72C5784B6FAF6F8 uses weak digest algorithm (SHA1)
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Calculating upgrade... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.