The error should not be swallowed and it should be instead propagated up
to calendar.get_upcoming_events, if it's called from that context. And
calendar.get_upcoming_events should be in charge of handling the
exceptions and make sure that failing to retrieve the events for one
calendar doesn't make the whole method fail.
- Using `@action` annotation to indicate methods that are allowed to be
executed as actions
- The output and errors of an action are automatically wrapped into a
`Response` object without any response build required on the plugin side