run-tests: ignore PermissionError when checking available ports
I'm not sure what this is, but I'm getting it occasionally when running in WSL.
When it was raised, none of the tests could run.
# __init__.py - Startup and module loading logic for Mercurial.
#
# Copyright 2015 Gregory Szorc <gregory.szorc@gmail.com>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
from __future__ import absolute_import
# Allow 'from mercurial import demandimport' to keep working.
import hgdemandimport
demandimport = hgdemandimport