How to check if the google access token has been revoked

Question

I'm using the google node js api to check a user's availability. How do I check to see if the user's access token has been revoked? I would like to send him an email if that's the case.

Here's what I have

    var defer = Q.defer(); // get a new deferral
    oauth2Client.setCredentials({
        refresh_token: refreshToken,
    });
    const calendar = google.calendar({version: "v3", auth: oauth2Client});

    calendar.freebusy.query(
        {
            auth: oauth2Client,
            resource: {
                timeMin: new Date(startDate).toISOString(),
                timeMax: new Date(endDate).toISOString(),
                items: [{id: "primary"}],
            },
        },
        (err, response) => {
            if (err) {
                console.dir(err);
                console.log(
                    "There was an error obtaining availability from google calendar service " +
                    err
                );
                defer.reject(err);
                return;
            }
            let events = null;
            if (
                response &&
                response.data &&
                response.data.calendars &&
                response.data.calendars.primary &&
                response.data.calendars.primary.busy
            ) {
                events = response["data"]["calendars"]["primary"]["busy"];
            }
            if (!events) {
                defer.resolve(false);
            } else {
                defer.resolve(events);
            }
        }
    );
    return defer.promise; // return a promise