Log Message:
py-virtualenv: updated to 16.7.7

v16.7.7:
Bugfixes
- * fix virtualenv creation when ``--no-pip`` argument used.
- upgrade bundled pip from ``19.3`` to ``19.3.1``

v16.7.6:
Bugfixes
- fix to support for Python 3 on MacOS 10.15 provided by Xcode
- bump bundled pip from ``19.2.3`` to ``19.3`` and setuptools from ``41.2.0`` to \ 
``41.4.0``