private function do_not_allowed($format)
 {
     dbsteward::$allow_function_redefinition = false;
     try {
         $this->build_db($format);
     } catch (Exception $e) {
         $this->assertEquals('function lpad with identical parameters is being redefined', $e->getMessage());
     }
     // make sure differencing doesn't want to do it either
     try {
         $this->upgrade_db($format);
     } catch (Exception $e) {
         $this->assertEquals('function lpad with identical parameters is being redefined', $e->getMessage());
     }
 }