/*
* 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) {