This port will be removed on 2020-12-31 if not fixed
You're right, and upstream knows the situation (same thing on many Linux distros). They are working on gdl-v1.0.0, which will depend on Python 3.x. v1.0.0-rc.3 has been out since June 19, but there remains some caveats: https://github.com/gnudatalanguage/gdl/issues
Switched to Python 3.6+ (commented out) in r557839