All subtests are failing with the same error: self = <webdriver.client.Session object at 0x7f7284747a50>, method = 'POST', url = 'session/2566af01-1686-4126-b8e9-59ffb880ccac/execute/sync' body = {'args': [], 'script': 'return window;'} def send_command(self, method, url, body=None): """ Send a command to the remote end and validate its success. :param method: HTTP method to use in request. :param uri: "Command part" of the HTTP request URL, e.g. `window/rect`. :param body: Optional body of the HTTP request. :return: `None` if the HTTP response body was empty, otherwise the `value` field returned after parsing the response body as JSON. :raises ValueError: If the response body does not contain a `value` key. :raises error.WebDriverException: If the remote end returns an error. """ response = self.transport.send( method, url, body, encoder=protocol.Encoder, decoder=protocol.Decoder, session=self) if response.status != 200: > raise error.from_response(response) E JavascriptErrorException: javascript error (500): JSON.stringify cannot serialize cyclic structures. body = {'args': [], 'script': 'return window;'} method = 'POST' response = <Response status=500 error=<JavascriptErrorException http_status=500>> self = <webdriver.client.Session object at 0x7f7284747a50> url = 'session/2566af01-1686-4126-b8e9-59ffb880ccac/execute/sync'