title: HTTP response for an unacceptable Accept header
body: <p>My RESTFul API can only respond JSON-encoded data (i.e. all my headers have <code>Content-Type: application/json</code>). What should I return, if the request has an <code>Accept</code> header that does not allow JSON (for example, <code>Accept: text/html</code>)? Should I just return a <code>400 Bad Request</code> with an explanation in the body, or is there a more specific status code for this exception?</p>
  
  <p>Note that this is different from <a href="https://stackoverflow.com/q/11973813/252239">unsupported request content-types</a>.</p>