"hint" message type

pilot/const/ipc.py

@@ -1,7 +1,8 @@
 MESSAGE_TYPE = {
     'verbose': 'verbose',
     'stream': 'stream',
-    'user_input_request': 'user_input_request',
-    'info': 'info',
+    'user_input_request': 'user_input_request',   # Displayed above the
+    'hint': 'hint',                        # Hint text, eg "Do you want to add anything else? If not, just press ENTER."
+    'info': 'info',                        # JSON data can be sent to progress `progress_stage`
     'local': 'local',
-}
+}