Configuration seems ok.
Was this application created with the 17-11 SDK, or updated from 17-8 for example?
The app was created before 17-11 SDK.
??? i cannot edit my post.
The app was created with whatever was up to date around 08.09.2017
Edit should be under "Actions", bottom left of your post.
Maybe the app is out of date, especially the grunt tasks which are in the /grunt folder of your app and some node-modules as well.
Did you update your app?