According to upstream realease notes, this port should work just fine with Python 3.
This port was restricted to Python 2.7 because its dependencies were lacking Python 3 support at that time (see https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219322).
We should test this port a bit and enable Python 3 if possible.
A commit references this bug:
Date: Tue Oct 13 21:59:24 UTC 2020
New revision: 552286
Give this port a bit more time to switch to Python 3
We just have to adjust the build process and do some tests, as Python 3 is
supported according to upstream.