ErrorOrNoticeMessage
The fields of an ErrorResponse (Tag 'E') or of a NoticeResponse (Tag 'N').
The two messages carry the same field set and differ only in their tag and in what severity says, so one class reads both. An error is returned from the stream and becomes an exception through ExceptionTranslator; a notice never leaves the stream and becomes a PgNotice there.
severity, localizedSeverity, code and message are the fields the protocol requires of either message; which of the rest arrive depends on what raised it.