enable_appstats

appengine_config.py
def webapp_add_wsgi_middleware(app):
  from google.appengine.ext.appstats import recording
  app = recording.appstats_wsgi_middleware(app)
  return app

appstats_SHELL_OK = True

app.yaml
[..]

handlers:
[..]
- url: /stats.*
  script: google.appengine.ext.appstats.ui.app

builtins:
[..]
- appstats: on