How to use the pyvirtualdisplay.abstractdisplay.XStartError function in PyVirtualDisplay

def test_color_xvfb():
    with pytest.raises(XStartError):
        vd = Display(color_depth=99).start().stop()
    vd = Display(color_depth=16).start().stop()
    vd = Display(color_depth=24).start().stop()
    vd = Display(color_depth=8).start().stop()

def test_stop_nostart():
    with pytest.raises(XStartError):
        Display().stop()

def stop(self):
        """
        stop display

        :rtype: self
        """
        if not self._is_started:
            raise XStartError("stop() is called before start().")

        self._redirect_display(False)

        if self.is_alive():
            try:
                try:
                    self._subproc.terminate()
                except AttributeError:
                    os.kill(self._subproc.pid, signal.SIGKILL)
            except OSError as oserror:
                log.debug("exception in terminate:%s", oserror)

            self._subproc.wait()
            self._read_stdout_stderr()
        if self._use_xauth:
            self._clear_xauth()

def start(self):
        """
        start display

        :rtype: self
        """
        if self._is_started:
            raise XStartError(self, "Display was started twice.")
        self._is_started = True

        if self._has_displayfd:
            self._start1()
        else:
            i = 0
            while True:
                try:
                    self._start1()
                    break
                except XStartError:
                    log.warning("start failed %s", i + 1)
                    time.sleep(0.05)
                    i += 1
                    if i >= self._retries:
                        raise XStartError(

def _wait_for_pipe_text(self, rfd):
        s = ""
        start_time = time.time()
        while True:
            (rfd_changed_ls, _, _) = select.select([rfd], [], [], 0.1)
            if not self.is_alive():
                raise XStartError(
                    "%s program closed. command: %s stderr: %s"
                    % (self._program, self._command, self.stderr)
                )
            if rfd in rfd_changed_ls:
                c = os.read(rfd, 1)
                if c == b"\n":
                    break
                s += c.decode("ascii")
            if time.time() - start_time >= _X_START_TIMEOUT:
                raise XStartTimeoutError(
                    "No reply from program %s. command:%s"
                    % (self._program, self._command,)
                )
        return s

:rtype: self
        """
        if self._is_started:
            raise XStartError(self, "Display was started twice.")
        self._is_started = True

        if self._has_displayfd:
            self._start1()
        else:
            i = 0
            while True:
                try:
                    self._start1()
                    break
                except XStartError:
                    log.warning("start failed %s", i + 1)
                    time.sleep(0.05)
                    i += 1
                    if i >= self._retries:
                        raise XStartError(
                            "No success after %s retries. Last stderr: %s"
                            % (self._retries, self.stderr)
                        )
                finally:
                    self._redirect_display(False)
        self._redirect_display(True)

break

                if exit_code != 0:
                    pass
                else:
                    log.info('Successfully started X with display "%s".', d)
                    ok = True
                    break

                if time.time() - start_time >= _X_START_TIMEOUT:
                    break
                time.sleep(_X_START_TIME_STEP)
            if not self.is_alive():
                log.warning("process exited early. stderr:%s", self.stderr)
                msg = "Failed to start process: %s"
                raise XStartError(msg % self)
            if not ok:
                msg = 'Failed to start X on display "%s" (xdpyinfo check failed, stderr:[%s]).'
                raise XStartTimeoutError(msg % (d, xdpyinfo.stderr))

        return self