Seems like the 2.0-alpha-4 Docker image didn't get pushed as was the alpha-3, it would be good to change/fix the release process so that that can't be forgotten.

As discussed yesterday, danielbeck and rtyler said it was probably because kohsuke's scripts may not have the Docker push part standardly built-in or something.

IMO, it's even more important those days where we want to maximize the number of testing against 2.x, and Docker makes it greatly easy to be sure to start over with a clean instance each time.