contrib/docker/ubuntu.template

rebase: fix issue 5494 also with --collapse

Differential Revision: https://phab.mercurial-scm.org/D2759

FROM ubuntu:__CODENAME__
RUN apt-get update && apt-get install -y \
  build-essential \
  debhelper \
  devscripts \
  dh-python \
  less \
  python \
  python-all-dev \
  python-docutils \
  unzip \
  zip