GTK error, failed building on command line

My guess is that the build script is trying to initialise X11 over the terminal, and failing. This only happens in the dev branch.


    ** (-c:27437): WARNING **: Command line `dbus-launch --autolaunch=613af6694c211a25d65930af0000001a --b
    inary-syntax --close-stderr' exited with non-zero exit status 1: Autolaunch error: X11 initialization
    failed.\n

    Traceback (most recent call last):

      File "<string>", line 16, in <module>

      File "/tmp/pip-mxUubW-build/setup.py", line 131, in <module>

        result = package.check()

      File "setupext.py", line 1428, in check

        success, msg = p.map(backend_gtk3agg_internal_check, [0])[0]

      File "/usr/lib/python2.7/multiprocessing/pool.py", line 227, in map

        return self.map_async(func, iterable, chunksize).get()

      File "/usr/lib/python2.7/multiprocessing/pool.py", line 528, in get

        raise self._value

    RuntimeError: Gtk couldn't be initialized