What happens when you develop a Python debugger and the latest Python version breaks it? We’ll go through the process of debugging a Python debugger and the methods we used to solve it efficiently. When a new Python version is released, the great opportunity to add new features to our software comes around. Yet, alongside those features, there’s always an API break which requires us to make undesired changes to our software. Often, the change can be as small and seemingly insignificant as a signature change or sometimes can be as big as shifting from Python 2 to 3.