Unable to add apt-repository in Ubuntu-18.04

Solution 1:

It is WebUpd8 team Atom PPA

sudo add-apt-repository ppa:webupd8team/atom
sudo apt-get update

Mind the ~ in your command.

Ehm, on 2nd reading: are you sure you copy/pasted this correctly?

You list 1 PPA and get an error on another PPA? If true, that seems fishy to me. If so the PPA is probably bugged. Might be an idea to report it on launchpad. Atom is NOT part of that PPA so it should NEVER tell you there is a problem related to the PPA belonging to Atom.

3rd: sudo add-apt-repository ppa:nilarimogard/webupd8 (Alin Andrei WebUpd8 PPA) works for me and does NOT show me an error.