That's all. We're done. That's one sequence: not particularly short; not particularly long.
The application runs on GAE here. (note code update)
And here are the final versions of passingkeys.py, index.html, and the app.yaml control file (which includes a mapping for these static source files).
This sequence cannot represent the intentions of the builders of Python, Django or the GAE implementation. It is only the story of my resolutions to my problems. It will only let you understand what I've done. But, you may find something useful for your application.
Of course, there are many problems with this sequence. It's not perfect. However, I believe that many such sequences, ironed-out, polished and improved, analyzed and argued over, can serve as inspiring resources for programmers. This practical, introspective approach may guide us to a future of smoother software development, for increasingly complex and coherent systems. It might also shape the future of tools and languages to support good engineering and design.
We only need to take nature's achievements seriously.