Update coverage to 4.5.4

[pyup-bot]

This PR updates coverage from 4.5.3 to 4.5.4.

Changelog

4.5.4

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

- Multiprocessing support in Python 3.8 was broken, but is now fixed.  Closes
`issue 828`_.

.. _issue 828: https://github.com/nedbat/coveragepy/issues/828


.. _changes_453:

Links

• PyPI: https://pypi.org/project/coverage
• Changelog: https://pyup.io/changelogs/coverage/
• Repo: https://github.com/nedbat/coveragepy

[codecov-io]

Codecov Report

❗ No coverage uploaded for pull request base (master@319ffa4). Click here to learn what that means.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             master   #142   +/-   ##
=======================================
  Coverage          ?   100%           
=======================================
  Files             ?     12           
  Lines             ?    116           
  Branches          ?      0           
=======================================
  Hits              ?    116           
  Misses            ?      0           
  Partials          ?      0

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[pyup-bot]

Closing this in favor of #205