In chapter 12, on page 256 (pdf) the last code snippet removes the catchErrorJustReturn method, and the decription states: “You also removed the catchErrorJustReturn() call to the observable returned by currentWeather(city:)”
Removing that causes the observable to be disposed after the first error received from the Web Service, and the driver then completes. Any other queries afterwards are not processed.
The source code for the next chapters keep catchErrorJustReturn in