Test CI build_geomodel_athena (and fix rendering of messages in the build script)

A CI pipeline failed in the build_geomodel_athena step in !416 (merged) due to a failed git rebase command. So I opened this MR to fix that.

However, I cannot reproduce that error. I suspect that was due to a temporary GitLab glitch.

However, while investigating that error, I fixed some errors in rendering messages in the build script. Their fix is now in this MR.