Scheduled weekly dependency update for week 43

[pyup-bot]

Update virtualenv from 20.8.1 to 20.9.0.

Changelog

20.9.0

~~~~~~~~~~~~~~~~~
- Fixed path collision that could lead to a PermissionError or writing to system
directories when using PyPy3.8 - by :user:`mgorny`. (`2182 <https://github.com/pypa/virtualenv/issues/2182>`_)
- Upgrade embedded setuptools to ``58.3.0`` from ``58.1.0`` and pip to ``21.3.1`` from ``21.2.4`` - by
:user:`gaborbernat`. (`2205 <https://github.com/pypa/virtualenv/issues/2205>`_)
- Remove stray closing parenthesis in activate.bat - by :user:`SiggyBar`. (`2221 <https://github.com/pypa/virtualenv/issues/2221>`_)

Links

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