Improve Twistlock Stage Scans

This template is ONLY used for enhancement requests. Bug reporting or new feature request issues should use the other template options for issue submission.

Current Behavior

Our Twistlock stage of the pipeline lacks advanced error handling. In the event Twistlock is unable to pull/retrieve the image, it logs the error in the json file output, but does not fail the stage.

Purpose

This would alert pipeline users of a failure in the Twistlock stage due to image retrieval issues and provide better feedback.

Plan

• We should parse Twistlock json output for any reference to "err" with a valid error message. (Possibly switch Harbor to read-only mode when testing to ensure failure to pull?)
• Output the "err" content in the pipeline job for the pipeline user.

Acceptance Criteria

• Verification that Twistlock stage will fail if there are any issues with image retrieval.