Update virtualenv to 16.7.7

[pyup-bot]

This PR updates virtualenv from 16.7.6 to 16.7.7.

Changelog

16.7.7

--------------------

Bugfixes
^^^^^^^^

- * fix virtualenv creation when ``--no-pip`` argument used. (`1430 <https://github.com/pypa/virtualenv/issues/1430>`_)
- upgrade bundled pip from ``19.3`` to ``19.3.1`` (`1433 <https://github.com/pypa/virtualenv/issues/1433>`_)

Links

• PyPI: https://pypi.org/project/virtualenv
• Changelog: https://pyup.io/changelogs/virtualenv/
• Homepage: https://virtualenv.pypa.io/