def METHOD_NAME(self, name, ok, msg=None, deltat=20):
    '''report a sensor error'''
    r = self.reports[name]
    if time.time() < r.last_report + deltat:
        r.ok = ok
        return
    r.last_report = time.time()
    if ok and not r.ok:
        self.say("%s OK" % name)
    r.ok = ok
    if not r.ok:
        self.say(msg)