The error seems to be specifically around App Engine apps accessing Google APIs. I&#x27;d guess that this is a failure regarding fetching credentials, like what&#x27;s described at <a href="https:&#x2F;&#x2F;developers.google.com&#x2F;api-client-library&#x2F;java&#x2F;google-api-java-client&#x2F;app-engine" rel="nofollow">https:&#x2F;&#x2F;developers.google.com&#x2F;api-client-library&#x2F;java&#x2F;google...</a>.