It maps the name of the config values that we use in our templates to
the name of the key in the snap config. This allows us to stick a
bunch of stuff in the questions namespace in the snap config, and to
use dashes, with minimal changes to our templates.
Drop Python 2 support, to fix tests.
Change-Id: I48b86b5e557e30f81e9cc415e7fa3a9133aa9f39
322514211b