I am trying to give the Google CDN service account access to my bucket as said here: https://cloud.google.com/cdn/docs/using-signed-urls
gsutil iam ch serviceAccount:service-{PROJECT_NUMBER}@cloud-cdn-fill.iam.gserviceaccount.com:objectViewer gs://{BUCKET}
But the response is:
BadRequestException: 400 Invalid argument
Adding it via the cloud console is also impossible, it says "Email addresses and domains must be associated with an active Google Account or Google Apps account."
Am I missing something or is this a bug?