Taking Uwe's original files and purely as an intellectual exercise re-writing the parser with a different algorithm and using OO and TDD (Test Driven Development). It doesn't work any better (except for the error reporting improvements already made on the main branch) but I got satisfaction from writing it. And being TDD it has unit tests now. And comments.
Written for vanilla Python 3.6 and Windows. To create the exe file run makeexe.bat which sets up a virtual environment 'env' containing PyInstaller and runs it.