[PATCH STABLE] docker: install less in Debian based distros

[Gregory Szorc]

# HG changeset patch
# User Gregory Szorc <gregory.szorc at gmail.com>
# Date 1493772374 25200
#      Tue May 02 17:46:14 2017 -0700
# Branch stable
# Node ID 3c3846ddf199cc96fb781f3fbd62570a3dc7087d
# Parent  fbb5f4bf94928b98fa87871e84bb2ef972ec2d51
docker: install less in Debian based distros

Without this, test-diff-color.t fails in Docker with a bunch of
"missing pager command 'less', skipping pager" warnings. That's
arguably a bug in the test itself not skipping if the pager isn't
available. But since we'll want to run this test in Docker and the
test requires a pager, installing `less` is not wrong: it just
doesn't fix the underlying problem.

diff --git a/contrib/docker/debian-jessie b/contrib/docker/debian-jessie
--- a/contrib/docker/debian-jessie
+++ b/contrib/docker/debian-jessie
@@ -4,6 +4,7 @@ RUN apt-get update && apt-get install -y
   debhelper \
   dh-python \
   devscripts \
+  less \
   python \
   python-all-dev \
   python-docutils \
diff --git a/contrib/docker/ubuntu.template b/contrib/docker/ubuntu.template
--- a/contrib/docker/ubuntu.template
+++ b/contrib/docker/ubuntu.template
@@ -4,6 +4,7 @@ RUN apt-get update && apt-get install -y
   debhelper \
   dh-python \
   devscripts \
+  less \
   python \
   python-all-dev \
   python-docutils \