sudo apt update

Hit:1 http://archive.canonical.com/ubuntu xenial InRelease
Hit:2 http://ppa.launchpad.net/openshot.developers/ppa/ubuntu xenial InRelease 
Hit:3 http://deb.opera.com/opera-stable stable InRelease                       
Hit:4 http://archive.ubuntu.com/ubuntu xenial InRelease                        
Ign:5 http://download.bitdefender.com/repos/deb bitdefender InRelease          
Hit:6 http://ppa.launchpad.net/pipelight/stable/ubuntu xenial InRelease        
Hit:7 http://download.bitdefender.com/repos/deb bitdefender Release      
Get:8 http://archive.ubuntu.com/ubuntu xenial-security InRelease [102 kB]
Get:9 http://archive.ubuntu.com/ubuntu xenial-updates InRelease [102 kB]
Fetched 204 kB in 1s (112 kB/s)                              
Reading package lists... Done
Building dependency tree       
Reading state information... Done
7 packages can be upgraded. Run 'apt list --upgradable' to see them.
W: http://download.bitdefender.com/repos/deb/dists/bitdefender/Release.gpg: Signature by key 639ADD458616BD06A1B55F9CA373FB480EC4FE05 uses weak digest algorithm (SHA1)