[Docs]Callback exception sends error msg to agent, not documented

[Oscar-Campo]

A message is sent automatically to the agent when an exception is raised from the callback.

Perhaps this must be written inside SDK documentation.

iottly-sdk-python/iottly_sdk/iottly.py

Lines 455 to 478 in 835feab

	def _wrapped_cb_execution(self, f):
	"""Wrap callback execution and send error to agent.
	"""
	if f is None:
	return None
	@wraps(f)
	def wrapper(*args, **kwargs):
	try:
	f(*args, **kwargs)
	except Exception as exc:
	exc_dump = json.dumps({
	'type': exc.__class__.__name__,
	'msg': str(exc)
	})
	# Format signal message
	exc_msg = Msg(
	payload=self._err_msg.format(exc_dump).encode(),
	type=True,
	channel=None
	)
	self._buffer.put(exc_msg) # En-quque msg blocking
	return wrapper