Autopilot FTBFS during override_dh_auto_test

[Łukasz Zemczak]

A rebuild of autopilot on zesty (1.4.1+17.04.20170305-0ubuntu1) fails to build.

The actual failure:

HOME=`mktemp -d --tmpdir=debian` \
XDG_RUNTIME_DIR=`mktemp -d --tmpdir=debian` \
python3 -m testtools.run discover autopilot.tests.unit
/usr/lib/python3.5/runpy.py:125: RuntimeWarning: 'testtools.run' found in sys.modules after import of package 'testtools', but prior to execution of 'testtools.run'; this may result in unpredictable behaviour
  warn(RuntimeWarning(msg))

terminate called after throwing an instance of 'std::runtime_error'
  what(): Unable to connect to user bus: Cannot autolaunch D-Bus without X11 $DISPLAY
Aborted (core dumped)
debian/rules:23: recipe for target 'override_dh_auto_test' failed

[Łukasz Zemczak (sil2100)]

After doing some blind experimenting, trying a build with an attached DISPLAY=:0.0 before the actual test command the build still fails with: "what(): Unable to connect to user bus: Failed to execute child process “dbus-launch” (No such file or directory)". Installing dbus-x11 (which has dbus-launch) makes it go forward but then I get some test failures that fail the build. Besides, I don't think built-time unit tests should really depend on having a graphical stack - certainly I wouldn't want to add the dbus-x11 build-dep without a really good reason.

Could anyone take a look at this?