class Xvfb(BackendServer):
    def __init__(self, display=':94'):
        super(Xvfb, self).__init__()
        self.display = display
    def start(self):
        self.log.info('Starting Xvfb on display %s', self.display)
        self.server = subprocess.Popen(
            [
                # fmt: off
                'Xvfb', self.display,
                '-screen', '0', '1280x1024x24',
                '-nolisten', 'tcp',
                '-nolisten', 'unix',
                # fmt: on
            ]
        )
    def __str__(self):
        return "<Xvfb {}>".format(self.display)