HTTPStatus returns the HTTP status code embedded in the error, or 500 (internal server error), if there was no specified status code.

StatusErrorDiff returns the empty string if the expected error string and status match err.

StatusErrorDiffRE returns the empty string if the expected error RE and status match err.

Error represents an error returned by Kivik.

CompositeError represents an HTTP status, encoded in the first byte as the status - 400, plus the error message.