When AWS API returns an error, the error message is not displayed to the user

Problem/Motivation

When a user submits a cache invalidation request using CloudfrontCacheInvalidateForm, and AWS API return a non-successful response code (e.g. 503), thus triggering an Exception, currently only a log message is added. The user should be notified when such error occurs.

Steps to reproduce

• Go to /admin/config/services/cloudfront-invalidate-url
• Submit an invalidation request by typing a URL and click Invalidate URL
• (You can simulate an AWS error by supplying a wrong key/secret)
• The success message "Cloudfront Cache invalidation is in progress. " displays instead of an error.

Proposed resolution

Display an error to the user when AWS API returns an error.

Remaining tasks

Write a patch to add a messenger->addError to display the error.

User interface changes

Display an error to the user when AWS API returns an error.