Cron job fails accessing url with admin_required decorator

According to the documentation Cron jobs should be allowed to access admin protected views. However I get a 302 error if I have the @admin_required decorator on the GET method.

In app.yaml I have defined this:

- url: /generator
  script: run.news.app
  login: admin

the view:

class GeneratorView(MethodView):
    @admin_required
    def get(self):
        return 'success', 200

urls.py

app.add_url_rule('/generator', 'generator', view_func=GeneratorView.as_view('generator'))

cron job:

cron:
- description: Scrape every 3 hours
  url: /generator
  schedule: every 3 hours synchronized

decorator:

def admin_required(func):
    """Requires App Engine admin credentials"""

    @wraps(func)
    def decorated_view(*args, **kwargs):
        if users.get_current_user():
            if not users.is_current_user_admin():
                abort(401)  # Unauthorized
            return func(*args, **kwargs)
        return redirect(users.create_login_url(request.url))

    return decorated_view

the funny part is, when I remove the admin_required decorator, the url is still admin-only protected because of login: admin in app.yaml.

However my unit test fails the authorization check because of the missing decorator.

def test_generator_fails_as_normal_user(self):
        self.setCurrentUser(u'john@example.com', u'123')
        rv = self.client.get('/generator')
        self.assertEqual(rv.status_code, 401)

AssertionError: 200 != 401

If I put the decorator back in, the unit test passes and cron job fails. Any suggestions?