add retain flag to mqtt example scripts

Author: abachman

examples/mqtt_client.py

@@ -31,7 +31,7 @@ def disconnected(client):
     print('Disconnected from Adafruit IO!')
     sys.exit(1)
 
-def message(client, feed_id, payload):
+def message(client, feed_id, payload, retain):
     # Message function will be called when a subscribed feed has a new value.
     # The feed_id parameter identifies the feed, and the payload parameter has
     # the new value.

examples/mqtt_subscribe.py

@@ -33,7 +33,7 @@ def disconnected(client):
     print('Disconnected from Adafruit IO!')
     sys.exit(1)
 
-def message(client, feed_id, payload):
+def message(client, feed_id, payload, retain):
     # Message function will be called when a subscribed feed has a new value.
     # The feed_id parameter identifies the feed, and the payload parameter has
     # the new value.

examples/mqtt_viewall.py

@@ -50,7 +50,7 @@ def on_connect(client, userdata, flags, rc):
 def on_disconnect(client, userdata, rc):
     print('Disconnected!')
 
-def on_message(client, userdata, msg):
+def on_message(client, userdata, msg, retain):
     print('Received on {0}: {1}'.format(msg.topic, msg.payload.decode('utf-8')))