Recently, the ndb graduated and its python module changed from ndb to google.appengine.ext.ndb. Webapp2 is bundled along with the SDK of appengine, but it seems they forgot to update some modules in it, and they still use the previous package.
I encountered it when I tried to debug my application locally, using the webapp2 user & authentication module, the application crashes from the bad import. When you deploy the application to the appengine server, you must provide a version of the webapp2, which overrides this problem (this worked as a workaround for me at least), thus the problem will not occur. But locally, you must go the installation directory of the appengine and delete it manually.
I spotted this bug roughly a month ago (23/12/2011), and there may be some fixes on the mainstream webapp2 release.
Update (18/2/2012): The problem still persists in version 1.6.2 of the appengine SDK for python.
Recently I was messing with Appengine’s pull queue and noticed the following. They did not offer a C/C++ API. All the other usual suspects are there, like python, Java, go, even PHP and Obj-C.
What happened to C/C++? It is not worth offering and maintaining any more an API for these two languages? Or google wants to promote go!, and pat the iOS developers with the Obj-C?
No, you cannot have a native app. That’s it! Maybe, because C/C++ do not offer by definition an HTTP protocol implementation.