Rob, this was a great exercise! This is new to me, so I ran into a couple of glitches. First, I had to make sure the usernames on my GitHub, Travis CI and DockerHub accounts were the all same, e.g., robdavis. When I did this exercise the first time, my DockerHub account name was different from GitHub and Travis, and the Travis failed to push the Docker image to Docker Hub. Second, after running the “heroku plugins:install heroku-container-registry” command, I had to run “heroku container:login;” otherwise, the “heroku container:push web” didn’t work.