Fix template ppa

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
update utility functions

breaking change: in subprocess module they've done away with DEVNULL.
That has been fixed along with additional improvements to
get_command_output and simplified what gets returned after execution.

added several container related functions to ease working with
those.

Signed-off-by: Adam Stokes <adam.stokes@ubuntu.com>
Update utils.py

Fixes remaining DEVNULL issue
Update gui.py

Fix keyerror in gui