dispatch: extract maybe-use-repr formatting to helper function
I think this makes the code much clearer. I had to think for a bit to
unpack the old-school `condition and if-true or if-false` dance, and
formatting argument lists here shouldn't be performance critical.
FROM ubuntu:__CODENAME__
RUN apt-get update && apt-get install -y \
build-essential \
debhelper \
dh-python \
devscripts \
python \
python-all-dev \
python-docutils \
zip \
unzip