Hope you have fixed this issue. Yes apple have not made it easy to migrate an older source, they support just the last version. To share the pain for context, we had projects in Swift 1.1, 2.1 and 3.x that we had to abandon or re-write due to these changes and supporting something that was already in production.
Sample code should be easy to convert, but in many cases not everything gets updated and you will still need to manually fix a couple of things. As an Author myself, I know the pain of upgrading sample code it can unfortunately lag, but I am sure as soon as there is a refresh (new version of the book), the code should be updated.