faisal:~$ sudo ppa-purge ppa:caffeine-developers/ppa
Updating packages lists
W: The repository 'http://ppa.launchpad.net/caffeine-developers/ppa/ubuntu xenial Release' does not have a Release file.
E: Failed to fetch http://ppa.launchpad.net/caffeine-developers/ppa/ubuntu/dists/xenial/main/binary-amd64/Packages  404  Not Found
E: Some index files failed to download. They have been ignored, or old ones used instead.
Warning:  apt-get update failed for some reason
faisal:~$