Ensure the universe repository is enabled
Ensure the universe repository is enabled

A minimal Ubuntu server installation might not have universe enabled by
default. By adding it, we ensure we can install packages only available
in universe, such as python3-pip

Merges #1650.

mail-in-a-box/mailinabox,mail-in-a-box/mailinabox,mail-in-a-box/mailinabox,mail-in-a-box/mailinabox