It seems Lua is the better choice for writing an asynchronous web micro-framework. I spent a lot of time trying to write a super minimal WSGI website in Python using nested generators and then realized I was wasting my time if I couldn't yield back to the body content iterator from anywhere in the call stack. uWSGI has an nginx plugin and support for Lua wsapi if anyone is interested:
http://projects.unbit.it/uwsgi/wiki/Lua