A "sorry, i did not understand" responder?

[mpadge]

@xuanxu We recently received an incorrectly formatted command which made us realise the importance of some kind of generic, "sorry, i did not understand that command" response. Would that be possible to implement? It took us four days to realise that something had gone wrong there, but a responder like that would have enabled immediate diagnosis.

[xuanxu]

Yes, this is something I have in my backlog for Buffy, I've just created an issue upstream.

[xuanxu]

Done and merged into the ropensci branch.
It should not need any change in the config file to work with the default response.