Created attachment 188526 [details] Patch Doxygen supports Python 3.x since 2015, don't limit python version with 2. Confirmed to build fine with DEFAULT_VERSIONS=python=3.6.
Patch looks good to me.
A commit references this bug: Author: amdmi3 Date: Mon Dec 4 20:12:21 UTC 2017 New revision: 455534 URL: https://svnweb.freebsd.org/changeset/ports/455534 Log: - Allow build with Python 3 PR: 224085 Approved by: cyberbotx@cyberbotx.com (maintainer) Changes: head/devel/doxygen/Makefile