The Terrain modifier diff has been adapted to work on latest master. A lot of code clean up was done in master, which is good
The diffs for the remove double modifiers to clean your meshes and imports are available for both 2.8 and 2.7. The video explaining the code will follow
Edit: the videos are up!
I was wondering can your course teach me how to code remove doubles modifier?
yes, it already shows you how to add a remove double modifier and much more