Hopefully, never.  ```post_move_from_storage_service``` is the hook for the LOM Space to talk to LOM.  Since the only thing that should be stored in LOM is AIPs, I don't want to tell LOCKSS about any non-AIP (or at least, non-package) files that are accidentally put in LOM Space.  Also, it expects ```package``` to actually exist (and calls functions on it), so this is a check to ensure it does.