Add debug logs and send websocket messages when the watch is closed
unexpectedly.
In addition to being helpful for debugging, the dashboard specifically
looks for a `resource.error` event containing the string "too old" in
order to trigger the watch to be resynced with a refreshed revision
number. Without this error returned, the dashboard will only see
`resource.stop` events and never change its behavior, continuing to try
to restart the watch with an incorrect resource version.
