message: Retry apt commands on connection timeout when building docker.
diff: set -e
  +# Retry on connection timeout.
  +bash -c "echo 'APT::Acquire::Retries \"3\";' > /etc/apt/apt.conf.d/80-retries"
  +
  # Install bootstrap dependencies from ubuntu deb repository.
  apt-get update
  apt-get install -y --no-install-recommends \
  