[rich90usa]

A coworker has has a small tool for accomplishing this: https://github.com/LesterTheTester/dfrnt

It has been integrated with Travis CI and GitHub pull requests so that non-passing diffs are appended as a comment to the pull request by a bot account.

If there's an intended diff, a pull request can also automatically be submitted against the original pull request which, on merge, updates the "gold master" images and allows the original pull request to pass.