def do_access_control(self):
        """`before_request` handler to check if user should be redirected to
        login page."""
        from abilian.services import get_service

        if current_app.testing and current_app.config.get("NO_LOGIN"):
            # Special case for tests
            user = User.query.get(0)
            login_user(user, force=True)
            return

        state = self.app_state
        user = unwrap(current_user)

        # Another special case for tests
        if current_app.testing and getattr(user, "is_admin", False):
            return

        security = get_service("security")
        user_roles = frozenset(security.get_roles(user))
        endpoint = request.endpoint
        blueprint = request.blueprint

        access_controllers = []
        access_controllers.extend(state.bp_access_controllers.get(None, []))

        if blueprint and blueprint in state.bp_access_controllers:
            access_controllers.extend(state.bp_access_controllers[blueprint])

        if endpoint and endpoint in state.endpoint_access_controllers:
            access_controllers.extend(state.endpoint_access_controllers[endpoint])

        for access_controller in reversed(access_controllers):
            verdict = access_controller(user=user, roles=user_roles)
            if verdict is None:
                continue
            elif verdict is True:
                return
            else:
                if user.is_anonymous:
                    return self.redirect_to_login()
                raise Forbidden()

        # default policy
        if current_app.config.get("PRIVATE_SITE") and user.is_anonymous:
            return self.redirect_to_login()
`before_request` handler to check if user should be redirected to
        login page.