API errors and media-types

"[email protected]" <[email protected]>
Newsgroups gmane.comp.web.services.rest
Message-ID <[email protected]>
Given that you have a specific media-type(s) for giving extended API errors e.g. application/vnd.andrei.error-v1+json, application/vnd.andrei.error-v2+json
which of the following do you find natural?

#1 Be specific about which error media-type(s) you can accept
GET http://.../resource
Accept: application/vnd.andrei.some-media-type-v1+json, application/vnd.andrei.error-v1+json
=>
409 CONFLICT
Content-Type: application/vnd.andrei.error-v1+json

#2 If the client lacks specification of an error media-type, assume that it can process the lowest/highest version
GET http://.../resource
Accept: application/vnd.andrei.some-media-type-v1+json
=>
409 CONFLICT
Content-Type: application/vnd.andrei.error-v2+json

#3 If the client lacks specification of an error media-type, do not return any media-type nor payload - just the HTTP status code
GET http://.../resource
Accept: application/vnd.andrei.some-media-type-v1+json
=>
409 CONFLICT

The thing is that for #1 and #3 to take place, basho's webmachine for instance would have to do content-negotiation again, but only for the media-types defined as error media-types and without throwing a 415 MEDIA TYPE NOT SUPPORTED.

Thank you for your time
Andrei

NB. I've posted the above and some more comments also at https://groups.google.com/forum/?hl=en&fromgroups#!topic/api-craft/7c4unolo8Rw and I'd want to pick your brain as well
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