How to install Pop Theme on Ubuntu 16.04 - E: Unable to locate package pop-theme

I'm trying to install Pop-theme, it's a great looking theme, and I really want to install it. The Github Repo outlines the steps I've already tried:

sudo add-apt-repository ppa:system76/pop
sudo apt-get update
sudo apt-get install pop-theme

I get E: Unable to locate package pop-theme

~$ sudo apt install pop-theme
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package pop-theme

Manual installation also gives the same issue. I also know its not a typo problem.

$ sudo apt install libsass0 sassc inkscape optipng libglib2.0-dev-bin
Reading package lists... Done
Building dependency tree       
Reading state information... Done
E: Unable to locate package sassc
E: Unable to locate package libglib2.0-dev-bin
E: Couldn't find any package by glob 'libglib2.0-dev-bin'
E: Couldn't find any package by regex 'libglib2.0-dev-bin'

The Repo says Supported Desktop Environments

* GNOME-Shell     >= 3.18.3
* GNOME-Flashback >= 3.18.2
* Budgie-Desktop  >= 10.2.7...

I have GNOME Shell 3.18.5, running Ubuntu-Gnome 16.04.