'start a timer to fire only once
like signal.alarm, but with better resolution than integer seconds.'

@mark.skipif((not hasattr(signal, 'setitimer')), reason='EINTR    tests    require    setitimer')
def alarm(self, t=None):

    if (t is None):
        t = self.signal_delay
    self.timer_fired = False
    self.orig_handler = signal.signal(signal.SIGALRM, self.stop_timer)
    signal.setitimer(signal.ITIMER_REAL, t, 1000)
