> pip install setuptools && pip install gpg --no-build-isolation
> do you have any idea what changed to require a new setuptools to be installed?
> My assumption is that whatever setuptools version is in use in the newest docker
> image is newer than or the same as a prior docker image where gpg 2.0.0 built ok.

The sole reason that setuptools is installed is because setuptools is required to build / install gpg.

I would think it's reasonable to assume that setuptools is newer now than whenever it was last built successfully. However it is not the cause for the failure, since setuptools are installed as the first thing anyway in the scripts/Docker/requirements.txt (setuptools >= 78.1.1)

> What does --no-build-isolation (NBI) do in this case? I am not installing into a virtual
> environment where I thought that was a useful flag. Does NBI prevent gpg from building
> in a virtual environment where it could be missing some components?

I am not exactly sure why but it fixes the build. It does however not work without it without the flag.
My best guess is that it would use some incompatible version from the isolated environment. With the flag I assume it is using the system provided environment that is compatible.

> 2) Do we expect the install to work in a venv?
> The docker image as it currently exists does not install/run Roundup in a venv. However, I have been experimenting with installing Roundup and its supporting modules in a venv.
> The base image sometimes has older versions of packages installed. While a newer release of the base image fixed this, I was using a newer version of these packages on the
> older base image and just hoped I didn't break any tools. By installing in a venv I isolate upgraded packages from the base image. Also I am adopting venv as the standard way to install
> Roundup. By using a venv in the Docker container I hope to reduce the documentation needed for other layouts by ignoring them 8-).

I have no idea about roundup, however I can say that gpg install fails the same way and has the same fix (using --no-build-isolation) in a python virtual environment.