Update isort to 4.3.8

[pyup-bot]

This PR updates isort from 4.3.5 to 4.3.8.

The bot wasn't able to find a changelog for this release. Got an idea?

Links

• PyPI: https://pypi.org/project/isort
• Changelog: https://pyup.io/changelogs/isort/
• Repo: https://github.com/timothycrosley/isort

[codecov]

Codecov Report

Merging #584 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #584   +/-   ##
=======================================
  Coverage   95.64%   95.64%           
=======================================
  Files          55       55           
  Lines        2850     2850           
=======================================
  Hits         2726     2726           
  Misses        124      124

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[pyup-bot]

Closing this in favor of #586