GAE的webapp2 i18n不承认django模板{% trans %}标签

I'm trying to add i18n capability to a little test project i'm working on. I'm using webapp2_extras i18n library. I have the locale folder with compiled translation .mo files created using the babel command-line. The app itself is just one simple django template and a main.py with one handler. When i'm using the gettext method right in the main I do get the translated text but strings inside the template that are wrapped with {% trans %} tag does not get translated. Here's the handler:I'm trying to add i18n capability to a little t