pkg/54530: devel/py-sysctl does not work with Python 3

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         54530
>Category:       pkg
>Synopsis:       devel/py-sysctl does not work with Python 3
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    pkg-manager
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Sep 07 17:20:00 +0000 2019
>Originator:     Andreas Gustafsson
>Release:        NetBSD-8.1, -9 branch, or -current
>Organization:

>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

The devel/py-sysctl module builds with Python 3, but importing
it fails.  It works with Python 2.

  $ pkg_info -a|grep sysctl 
  py37-sysctl-0.1nb1  Python interface to sysctl(3)
  py27-sysctl-0.1nb1  Python interface to sysctl(3)
  $ python2.7 -c 'import sysctl'
  $ python3.7 -c 'import sysctl'
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
  ModuleNotFoundError: No module named 'sysctl'
  $

>How-To-Repeat:

  cd /usr/pkgsrc/devel/py-sysctl
  make install
  python3.7 -c 'import sysctl'

>Fix: