function handle503Error(fnError0) {
			return function (oErrorResponse) {
				if (that.checkAndProcessRetryAfterError(oRequest, oErrorResponse, fnSuccess, fnError0, oHandler,
						oHttpClient, oMetadata, oRequestHandle, bSkipHandleTracking)) {
					return;
				}
				fnError0(oErrorResponse);
			};
		}
Wraps the OData.request method and keeps track of pending requests.

@param {object} oRequest The request object
@param {function} fnSuccess Success callback function
@param {function} fnError Error callback function
@param {object} oHandler The request handler object
@param {object} oHttpClient The HttpClient object
@param {object} oMetadata The metadata object
@param {boolean} [bSkipHandleTracking] Whether the request is excluded from the tracking of request handles
@returns {object} The request handle
@private