Yeah, this is a bit of a pet peeve of mine. I've seen a lot of Python app Docker images which are built by just copying the git repo straight into the image. Better to build a package from the source in one CI step, and then install that package into the deploy image in another.
Overall, two-phase docker build is a much better model that avoids a lot of miscellaneous issues, including this one. But its also not super well-known for devs who just touch docker every now and then.
