Google Cloud Platform or Google App Engine 'gcloud app deploy' not updating your app? Debugger not working?

If you use python, and occasionally run your app locally, you'll notice some files that are generated: .pyc and index.yaml. If you accidentally 'gcloud app deploy' these files, especially when you have not run it locally for a while, they can break your application! Or drive you crazy!

In particular, they break the Google Cloud Console debugger (formerly the stackdriver debugger)  ... so while you're trying to figure out why your application doesn't work as expected, the debugger keeps telling you that you're setting logpoints on non-existent lines of code!

What has happened, is that Google is not checking to see whether the .py source file and the .pyc file match. It would be very nice if they did this. They could just check the timestamps. It would be easy. But they don't. 

And you keep changing your source code in trivial ways, perhaps adding some logging to see what's going on, but the live deployed application doesn't change. And the debugger doesn't work!

The fix is obvious: delete the .pyc and index.yaml files. Or put them in your .gcloudignore file.

I hope this helps someone. :-)