init function of Stemmer returned uninitialized object

Describe the bug
I am using FreeBSD 12.1_9, I am just updating ports using portmaster. I get this problem with cmake update. This is my log:

Sphinx version: 3.2.1
Python version: 3.7.9 (CPython)
Docutils version: 0.15.2 release
Jinja2 version: 2.10.1
Last messages:

Loaded extensions:
Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/sphinx/cmd/build.py", line 279, in build_main
args.tags, args.verbosity, args.jobs, args.keep_going)
File "/usr/local/lib/python3.7/site-packages/sphinx/application.py", line 240, in init
self.setup_extension(extension)
File "/usr/local/lib/python3.7/site-packages/sphinx/application.py", line 398, in setup_extension
self.registry.load_extension(self, extname)
File "/usr/local/lib/python3.7/site-packages/sphinx/registry.py", line 409, in load_extension
mod = import_module(extname)
File "/usr/local/lib/python3.7/importlib/init.py", line 127, in import_module
return _bootstrap._gcd_import(name[level:], package, level)
File "", line 1006, in _gcd_import
File "", line 983, in _find_and_load
File "", line 967, in _find_and_load_unlocked
File "", line 677, in _load_unlocked
File "", line 728, in exec_module
File "", line 219, in _call_with_frames_removed
File "/usr/local/lib/python3.7/site-packages/sphinx/builders/epub3.py", line 20, in
from sphinx.builders import _epub_base
File "/usr/local/lib/python3.7/site-packages/sphinx/builders/_epub_base.py", line 25, in
from sphinx.builders.html import BuildInfo, StandaloneHTMLBuilder
File "/usr/local/lib/python3.7/site-packages/sphinx/builders/html/init.py", line 39, in
from sphinx.search import js_index
File "/usr/local/lib/python3.7/site-packages/sphinx/search/init.py", line 125, in
from sphinx.search.en import SearchEnglish
File "/usr/local/lib/python3.7/site-packages/sphinx/search/en.py", line 14, in
from sphinx.util.stemmer import get_stemmer
File "/usr/local/lib/python3.7/site-packages/sphinx/util/stemmer/init.py", line 14, in
from Stemmer import Stemmer as _PyStemmer
SystemError: init function of Stemmer returned uninitialized object

To reproduce the error:

$sudo portmaster cmake

Start with sphinx/util/stemmer/init.py and the traceback's import of Stemmer as _PyStemmer; determine whether the failure is in Sphinx or the installed dependency on FreeBSD. Reproduce with the reported Sphinx, Python, and Docutils versions and sudo portmaster cmake. Done means identifying the responsible compatibility issue and confirming a working build or a documented limitation.