Update flake8 to 3.7.9

[pyup-bot]

This PR updates flake8 from 3.7.7 to 3.7.9.

Changelog

3.7.8

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

You can view the `3.7.8 milestone`_ on GitLab for more details.

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

- Fix handling of ``Application.parse_preliminary_options_and_args`` when
argv is an empty list (See also `GitLab!310`_, `GitLab518`_)

- Fix crash when a file parses but fails to tokenize (See also `GitLab!314`_,
`GitLab532`_)

- Log the full traceback on plugin exceptions (See also `GitLab!317`_)

- Fix `` noqa: ...`` comments with multi-letter codes (See also `GitLab!326`_,
`GitLab549`_)


.. all links
.. _3.7.8 milestone:
 https://gitlab.com/pycqa/flake8/milestones/31

.. issue links
.. _GitLab518:
 https://gitlab.com/pycqa/flake8/issues/518
.. _GitLab532:
 https://gitlab.com/pycqa/flake8/issues/532
.. _GitLab549:
 https://gitlab.com/pycqa/flake8/issues/549

.. merge request links
.. _GitLab!310:
 https://gitlab.com/pycqa/flake8/merge_requests/310
.. _GitLab!314:
 https://gitlab.com/pycqa/flake8/merge_requests/314
.. _GitLab!317:
 https://gitlab.com/pycqa/flake8/merge_requests/317
.. _GitLab!326:
 https://gitlab.com/pycqa/flake8/merge_requests/326

Links

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