testing: fix typo

[tych0]

Got another CI failure from an overloaded host (how is 20 seconds not enough?!):

https://github.com/tych0/xcffib/runs/7490425253?check_suite_focus=true

---

self = <test.conftest.XcffibTest object at 0x7ff1b4899d00> def setUp(self): self._old_display = os.environ.get('DISPLAY') self._display, self._display_lock = find_display() os.environ['DISPLAY'] = ':%d' % self._display self._xvfb = self.spawn(self._xvfb_command()) if self.xtrace: subprocess.Popen(['xtrace', '-n'])

xtrace's default display is :9; obviously this won't work

        # concurrently, but it's not the default so...
        os.environ['DISPLAY'] = ':9'
    try:
        self.conn = self._connect_to_xvfb()
    except AssertionError:

      self._restore_dislpay()

E AttributeError: 'XcffibTest' object has no attribute '_restore_dislpay'

I ran mypy, and it doesn't seem to catch this one either, for some reason. damn.

Signed-off-by: Tycho Andersen tycho@tycho.pizza

[tych0]

> assert False, "couldn't connect to xvfb"

Huh, something has changed recently (or github actions is all the sudden much more overloaded), because I'm getting this a lot now.