Although port has DOCS option, DOCSDIR and PORTDOCS set, and PORTDOCS created, no docs are actually installed. Either some docs should be installed, or these unused bits removed.
Also you should probably change MAINTAINER to your FreeBSD email address for all your ports.
A commit references this bug: Author: amdmi3 Date: Thu Sep 3 10:28:16 UTC 2015 New revision: 395944 URL: https://svnweb.freebsd.org/changeset/ports/395944 Log: - Remove everything related to DOCS as not documentation is actually installed - Sort USE_PYTHON PR: 200620 Submitted by: amdmi3 Approved by: maintainer timeout (wenheping@gmail.com, 3 months) Changes: head/math/py-pymc/Makefile