This came up in a discussion with Ivan Herman about how RDF-emitting web 
services (e.g. his RDFa distiller) should behave when an error occurs.

It seems that Tabulator is not programmed to do anything with the response body 
in the case where the HTTP status code indicates an error. That's poor behaviour 
-- the HTTP spec says: “Client Error 4xx: ... User agents SHOULD display any 
included entity to the user.”

I made a URI that returns a 400 error and a single N3 triple in the response 
body:

http://richard.cyganiak.de/2009/01/400.php

I would expect the triple to be shown somehow to the user:

[] <http://example.com/error> "Bad request!"

But instead I just get a generic HTTP error message.