add a point via latitude/longitude

def create_and_append_rally_point(self, lat, lon, alt, break_alt, land_dir, flags):
        '''add a point via latitude/longitude'''
        p = mavutil.mavlink.MAVLink_rally_point_message(self.target_system, self.target_component,
                                                        self.rally_count(), 0, lat, lon, alt, break_alt, land_dir, flags)
        self.append_rally_point(p)