Use Ubuntu 16.04 as oldest testbed on travis

This needed a few tweaks to the docker file worth mentioning:
- tzdata is not installed by default, resulting in test-gnc-timezone to fail
- there were a couple of debconf warnings
  * missing apt-utils package => added it to the list
  * no interactive terminal for autoremove => forced non-interactive mode
- in addition I have made building the docker file more verbose in order
  to catch such issues more easily in the future. If this turns out to be
  too distracting I can undo that part again.

.travis.yml

@@ -4,7 +4,7 @@ language: c++
 compiler: gcc
 env:
     - BUILDENV=arch BUILDTYPE=cmake-ninja
-    - BUILDENV=ubuntu-14.04 BUILDTYPE=cmake-make
+    - BUILDENV=ubuntu-16.04 BUILDTYPE=cmake-make
 services:
     - docker
 install:

util/ci/ubuntu-14.04-docker

@@ -1,10 +0,0 @@
-from ubuntu:14.04
-run sed -i"" "s/^# deb-src/deb-src/" /etc/apt/sources.list
-run apt-get update -qq
-run apt-get build-dep -qq gnucash > /dev/null
-run apt-get install -qq git bash-completion cmake3 make swig xsltproc libdbd-sqlite3 texinfo ninja-build libboost-all-dev libgtk-3-dev libwebkit2gtk-3.0-dev > /dev/null
-run apt-get --reinstall install -qq language-pack-en language-pack-fr
-run git clone https://github.com/google/googletest -b release-1.8.0 gtest
-copy ubuntu-14.04-testscript afterfailure commonbuild /
-run chmod +x /ubuntu-14.04-testscript /afterfailure /commonbuild
-entrypoint /ubuntu-14.04-testscript

util/ci/ubuntu-16.04-docker

@@ -0,0 +1,19 @@
+from ubuntu:16.04
+# Travis' ubuntu docker images don't have any package sources enabled by default
+# So start by enabling what we need
+run sed -i"" "s/^# deb-src/deb-src/" /etc/apt/sources.list
+run apt-get update -y
+# Note all apt-get commands will be run with DEBIAN_FRONTEND=noninteractive
+# to silence a bunch of warnings
+# See https://stackoverflow.com/questions/22466255/is-it-possible-to-answer-dialog-questions-when-installing-under-docker for details
+# And install apt-utils to silence another set of warnings
+# See https://github.com/phusion/baseimage-docker/issues/319 for a similar discussion
+run DEBIAN_FRONTEND=noninteractive apt-get install -y --no-install-recommends apt-utils
+run DEBIAN_FRONTEND=noninteractive apt-get upgrade -y
+run DEBIAN_FRONTEND=noninteractive apt-get build-dep -y gnucash
+run DEBIAN_FRONTEND=noninteractive apt-get install -y git bash-completion cmake make swig xsltproc libdbd-sqlite3 texinfo ninja-build libboost-all-dev libgtk-3-dev libwebkit2gtk-3.0-dev tzdata
+run DEBIAN_FRONTEND=noninteractive apt-get --reinstall install -y language-pack-en language-pack-fr
+run git clone https://github.com/google/googletest -b release-1.8.0 gtest
+copy ubuntu-16.04-testscript afterfailure commonbuild /
+run chmod +x /ubuntu-16.04-testscript /afterfailure /commonbuild
+entrypoint /ubuntu-16.04-testscript