Debugging Jinja2 templates in Google App Engine

Jinja2 needs some python modules that are forbidden in the python sandbox provided by Google App Engine. Fortunately its fairly easy to white list them in the SDK local development server — currently there is no workaround for production.

PRODUCTION = not os.environ.get('SERVER_SOFTWARE', '').startswith('Dev')
if not PRODUCTION:
    # enable jinja2 debugging info in GAE SDK
    from google.appengine.tools.devappserver2.python import sandbox
    sandbox._WHITE_LIST_C_MODULES += ['_ctypes', 'gestalt']

The original workaround is not working on the new development server aka devappserver2.