I should note that Google Groups is reserved for general product discussions and not for reporting issues. Issue Tracker is for reporting Google Cloud Platform-end issues and feature requests.
So, I recommend that you report this issue in the Issue Tracker and run the “gcloud app deploy” command with the “--verbosity=debug” and also “gcloud info” with --anonymize parameter to provide us the stack trace and your information about the current gcloud environment there so that we would be able to investigate the issue root cause.
You may follow the Quickstart in your desired programming language to double-check the steps you have taken to deploy your application.