Thank you! That helped me fix my issue.
The solution was to simply remove the ENTRYPOINT instruction. I had thought that ENTRYPOINT ["/bin/sh", "-c"] was equivalent to the default, but I guess not.
I had specified that because I had noticed that when doing docker run -i -t python:2.7, I started in a python interpreter, so so I thought (mistakenly) that I needed to override ENTRYPOINT. I hadn’t looked at the Dockerfile for that image, and had I done so I would have seen that python2 was the CMD.
Thanks again!
Mark