How to use the pywatchman.compat.reraise function in pywatchman

deadline = time.time() + self.start_timeout
        while time.time() < deadline:
            try:
                client = pywatchman.client(sockpath=self.sock_file)
                self.pid = client.query("get-pid")["pid"]
                break
            except pywatchman.SocketConnectError:
                t, val, tb = sys.exc_info()
                time.sleep(0.1)
            finally:
                client.close()

        if self.pid is None:
            # self.proc didn't come up: wait for it to die
            self.stop()
            pywatchman.compat.reraise(t, val, tb)