I got some data corruption errors when trying this chapter.
SQLLite databases have the default option to use journaling.
I fixed this in the CoreDataStack by setting the journal_mode to DELETE:
lazy var storeDescription: NSPersistentStoreDescription = {
let description = NSPersistentStoreDescription(url: self.storeURL)
description.setValue("DELETE" as NSObject, forPragmaNamed: "journal_mode")
description.shouldMigrateStoreAutomatically = true
description.shouldInferMappingModelAutomatically = false
return description
}()