Debian users may leverage the same source as the Ubuntu PPA.
Add the following line to /etc/apt/sources.list`:
deb http://ppa.launchpad.net/ansible/ansible/ubuntu trusty main
Set apt keys
$ sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 93C4A3FD7BB9C367
$ sudo apt update
$ sudo apt install ansible