Update tox to 3.27.0

[pyup-bot]

This PR updates tox from 3.26.0 to 3.27.0.

Changelog

3.27.0

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

Bugfixes
^^^^^^^^

- Dropped ``--build-option`` in isolated builds, an alternative fix for the ``SetuptoolsDeprecationWarning`` about using ``--global-option`` -- by :user:`adamchainz`
`2497 <https://github.com/tox-dev/tox/issues/2497>`_
- Remove read-only files in ``ensure_empty_dir``.
`2498 <https://github.com/tox-dev/tox/issues/2498>`_
- Multiple tox instances no longer clobber the ``.tox`` directory when
``provision_tox_env`` is used. - by :user:`masenf`
`2515 <https://github.com/tox-dev/tox/issues/2515>`_


Documentation
^^^^^^^^^^^^^

- Clarify that ``install_command`` only takes one command - by :user:`jugmac00`
`2433 <https://github.com/tox-dev/tox/issues/2433>`_
- Documented problems with plugin and provision env - by :user:`ziima`.
`2469 <https://github.com/tox-dev/tox/issues/2469>`_

Links

• PyPI: https://pypi.org/project/tox
• Changelog: https://pyup.io/changelogs/tox/
• Docs: https://tox.readthedocs.io