Some of the libraries featured in the book have been updated recently, which is a good thing - it means you're learning to use Python packages that are steadily being improved. When packages are updated you have the option of using the version that was featured in the book, which lets you run code exactly as it's written in the book. You can also choose to install the latest version of each package, and modify the code in the book slightly. Each approach is outlined clearly in these updates.
Pygal has been updated to version 2. You can install a version of Pygal that runs the code exactly as it's written in the book, or you can install the latest version of Pygal and modify what's in the book slightly. See installing Pygal, and see the updates to Chapter 15 to make tooltips appear on charts.
Pygal's world map and internationalization features have been moved to a separate module. See the section on installing Pygal, and see the specific updates for Chapter 16.
The updates to Chapter 17 allow tooltips to show on charts generated with Pygal.