See this thread: #31233 (comment)

(Actually, while testing, a missing python is now a hard error already when -DBUILD_GUI=ON. So I don't think the wording "refactor" accurately represents the changes here.)

This bug still exists. rm -rf ./bld-cmake && cmake -B ./bld-cmake -DBUILD_GUI=ON now fails with:

So it would be good to revert this pull, or adjust the docs:

We need to decide whether to document the GUI dep, or re-adjust the code. cc @hebasto