Problem described
rosserial_python : Service handler returned None
https://github.com/ros-drivers/rosserial/issues/408
Solution described
https://github.com/ros-drivers/rosserial/pull/414
https://github.com/ros-drivers/rosserial/commit/5e4e6db497b89f752c792bda5fddf1cadd1a79f0
Version confirmed
inaciose@ideapad:~/tmp$ rosversion rosserial_arduino
0.8.0
Solution applied
vi /opt/ros/melodic/lib/python2.7/dist-packages/rosserial_python/SerialClient.py
line 173, 174, abd 175 replaced by:
self.parent.send(self.id, data_buffer.getvalue()) while self.response is None: time.sleep(0.001)