We cannot get rid of this error - we upgraded to XCode 9.3 and we have the icon in all places requested. We still get this error with every submission:
We identified one or more issues with a recent delivery for your app, "xxxxx". Your delivery was successful, but you may wish to correct the following issues in your next delivery:
Missing App Store Icon - WatchOS Apps must include a 1024x1024px App Store Icon in PNG format. Without providing the icon in the Asset Catalog or via App Store Connect, apps cannot be submitted for App Review or Beta App Review. Refer to https://developer.apple.com/watchos/human-interface-guidelines/icons-and-images/home-screen-icons/ for more information.
After you’ve corrected the issues, you can use Xcode or Application Loader to upload a new binary to iTunes Connect.
The App Store Team