This service runs as a Google Managed VM.
Use the gcloud tool to deploy:

$ gcloud --project symbolic-datum-552 preview app deploy --no-promote app.yaml

Then use the Cloud Console to set the new version as the default,
and delete the old instance (lest it keep running):
https://cloud.google.com/console/appengine/versions?project=symbolic-datum-552&moduleId=pushback