code: function(error){
              var event = {
                  cnf:conf,
                  req:options,
                  error:error||{}
              };
              // check global error handler
              dispatch.call(this,'error',event);
              if (event.stopped){
                  return;
              }
              // dispatch error config event
              var onerror = options.onerror||conf.onerror||'onerror';
              if (_u._$isFunction(onerror)){
                  onerror.call(this,event);
              }else if(_u._$isString(onerror)){
                  this._$dispatchEvent(onerror,event);
              }
          }
docs: onerror event