selfcheck.py: add checking map->base_link tf transform

clover/src/selfcheck.py

@@ -485,6 +485,9 @@ def check_local_position():
             failure('roll is %.2f deg; place copter horizontally or redo level horizon calib',
                     math.degrees(roll))
 
+        if not tf_buffer.can_transform('base_link', pose.header.frame_id, rospy.get_rostime(), rospy.Duration(0.5)):
+            failure('can\'t transform from %s to base_link (timeout 0.5 s): is TF enabled?', pose.header.frame_id)
+
     except rospy.ROSException:
         failure('no local position')