Add warning log for NoWorkingDeviceConnectionError in update_config

Author: mn-ram

openwisp_controller/connection/tasks.py

@@ -76,7 +76,11 @@ def update_config(device_id):
     try:
         try:
             device_conn = DeviceConnection.get_working_connection(device)
-        except NoWorkingDeviceConnectionError:
+        except NoWorkingDeviceConnectionError as e:
+            logger.warning(
+                f"update_config for device {device_id}: "
+                f"DeviceConnection.get_working_connection failed: {e}"
+            )
             return
         else:
             logger.info(f"Updating {device} (pk: {device_id})")