Static analysis showed some unused variables and imports, and running the code in Python 3.9 revealed a few invalid escapes (previous versions of Python silently "fixed" these, so the code change here will not affect the results).
git-svn-id: https://free-cad.svn.sourceforge.net/svnroot/free-cad/trunk@5000 e8eeb9e2-ec13-0410-a4a9-efa5cf37419d