/*
 * Retrieve error from last call to MusicBrainz::Client#query with this MusicBrainz::Client object.
 *
 * Aliases:
 *   MusicBrainz::Client#get_error
 *   MusicBrainz::Client#get_query_error
 *
 * Example:
 *   # simple query and error return
 *   query = MusicBrainz::Query::GetStatus
 *   puts 'Error: ' << mb.error unless mb.query query
 *
 */
static VALUE mb_client_error(VALUE self) {