add-apt-repository command not found

Problem

I was trying to add an PPA repository and got this error on a server:

$ sudo add-apt-repository ppa:blah/foobar
sudo: add-apt-repository: command not found

Solution

The add-apt-repository comes from the software-properties-common package. Installing it solved the problem:

$ sudo apt install software-properties-common

Tried with: Ubuntu 16.04