Pkgsrc python cannot import SemLock on CentOS

[Jason Bacon <outpaddling%yahoo.com@localhost>]

Anyone know how to get around this?  It's hit me a couple of times now 
in applications I'd really
like to deploy via pkgsrc.

Yum's python imports fine, but I've seen this issue with multiple 
versions of pkgsrc python.

It's not true that the platform lacks a functioning sem_open().

Thanks,

    JB

Pkgsrc python:

Linux centosdev.ceas  bacon ~ 1019: python3.7
Python 3.7.0 (default, Oct 15 2018, 04:47:22)
[GCC 6.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import multiprocessing
>>> from multiprocessing import synchronize
Traceback (most recent call last):
  File "/usr/pkg/lib/python3.7/multiprocessing/synchronize.py", line 
29, in <module>
    from _multiprocessing import SemLock, sem_unlink
ImportError: cannot import name 'SemLock' from '_multiprocessing' 
(/usr/pkg/lib/python3.7/lib-dynload/_multiprocessing.so)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/pkg/lib/python3.7/multiprocessing/synchronize.py", line 
33, in <module>
    " synchronization primitives needed will not" +
ImportError: This platform lacks a functioning sem_open implementation, 
therefore, the required synchronization primitives needed will not 
function, see issue 3770.
>>>

Yum python:

Linux centosdev.ceas  bacon ~ 1019: /usr/bin/python
Python 2.7.5 (default, Jul 13 2018, 13:06:57)
[GCC 4.8.5 20150623 (Red Hat 4.8.5-28)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import multiprocessing
>>> from multiprocessing import synchronize
>>>

Linux centosdev.ceas  bacon ~ 1020: uname -a
Linux centosdev.ceas.uwm.edu 3.10.0-693.11.1.el7.x86_64 #1 SMP Mon Dec 4 
23:52:40 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
Linux centosdev.ceas  bacon ~ 1022: cat /etc/redhat-release
CentOS Linux release 7.5.1804 (Core)