Setup initial requirements for daemon run.

def _prepare(self):
        """ Setup initial requirements for daemon run.
            """

        super(TaskRunner, self)._prepare()
        self._setup_root_plugins()

        # set the default x-window display for non-mac systems
        if not sys.platform.lower().startswith('darwin'):
            if not 'DISPLAY' in os.environ:
                os.environ['DISPLAY'] = ':0.0'