Google App Engine and win32 DDE
The problem was not on the GAE development server: I managed to uninstall the win32 python build 216 library and install a previous version. The problem was indeed with the manifest of the build 216 and not with the GAE development server. Now it works fine with build 214.
I'm trying to set up a little server through the App Engine Python development server:
GOAL:
On Windows I've got a DDE application.
I need to read data from this application and serve it over the Internet.
SITUATION:
The development server is working correctly on port 80, enabling me to store data and make it available as JSON over the Internet.
PROBLEM:
I cannot get the development server to work correctly with the win32 Python library.
I enabled the module in the local whitelist, but still when trying to start a DDE connection it says:

This must be an MFC application - try loading win32ui first 
      args = ('This must be an MFC application - try loading win32ui first',) 
      message = 'This must be an MFC application - try loading win32ui first'

I have got no idea on what to do. Any hint will be very much appreciated.