Wait for the vehicle to become armable.

        If timeout is nonzero, raise a TimeoutError if the vehicle
        is not armable after timeout seconds.

def wait_for_armable(self, timeout=None):
        '''Wait for the vehicle to become armable.

        If timeout is nonzero, raise a TimeoutError if the vehicle
        is not armable after timeout seconds.
        '''

        def check_armable():
            return self.is_armable

        self.wait_for(check_armable, timeout=timeout)