Update flake8 to 3.8.3

[pyup-bot]

This PR updates flake8 from 3.8.2 to 3.8.3.

Changelog

3.8.3

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

You can view the `3.8.3 milestone`_ on GitLab for more details.

Bugs Fixed
~~~~~~~~~~

- Also catch ``SyntaxError`` when tokenizing (See also `GitLab!433`_,
`GitLab662`_)

- Fix ``--jobs`` default display in ``flake8 --help`` (See also `GitLab!434`_,
`GitLab665`_)

.. all links
.. _3.8.3 milestone:
 https://gitlab.com/pycqa/flake8/-/milestones/36

.. issue links
.. _GitLab662:
 https://gitlab.com/pycqa/flake8/issues/662
.. _GitLab665:
 https://gitlab.com/pycqa/flake8/issues/665

.. merge request links
.. _GitLab!433:
 https://gitlab.com/pycqa/flake8/merge_requests/433
.. _GitLab!434:
 https://gitlab.com/pycqa/flake8/merge_requests/434

Links

• PyPI: https://pypi.org/project/flake8
• Changelog: https://pyup.io/changelogs/flake8/
• Repo: https://gitlab.com/pycqa/flake8