Deploy fails if staging bucket does not exist

[chanseokoh]

I know it used to work, but it fails on my existing GCP projects as well as a new GCP project:

"error": {
  "errors": [
   {
    "domain": "global",
    "reason": "forbidden",
    "message": "Caller does not have storage.objects.list access to bucket bbb.",
    "debugInfo": "com.google.net.rpc3.RpcException: cloud.bigstore.ResponseCode.ErrorCode::ACCESS_DENIED: ACCESS_DENIED: ACCESS_DENIED: