IOExceptions no matter what on deploying to appspot

[Rashmi S]

I've been working on a GAE project(Spring MVC based) which works perfectly in eclipse, localhost. I'm using google's recaptcha on subscribe form. I also use SendGrid's service-free version- for sending mail. The point is the code works perfectly in eclipse but fails with IOException on deploying on App Engine Standard. I've no clue why. I'm tired trying to figure this out. 

[George (Cloud Platform Support)]

How did you deploy your app? Did you deploy it using Eclipse? Was it through maven, or by running gcloud app deploy? 

What happens if you deploy your app with gcloud app deploy --verbosity=debug ? 

You are encouraged to deploy the app given on the "Deploy Spring Boot Application in App Engine standard" page in the same way as your own app, and report any differences in behavior, once deployed.