⬆️ Bump coverage from 5.0.3 to 5.0.4 (#80)

Bumps [coverage](https://github.com/nedbat/coveragepy) from 5.0.3 to 5.0.4.
- [Release notes](https://github.com/nedbat/coveragepy/releases)
- [Changelog](https://github.com/nedbat/coveragepy/blob/master/CHANGES.rst)
- [Commits](nedbat/coveragepy@coverage-5.0.3...coverage-5.0.4)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

requirements_test.txt

@@ -1,5 +1,5 @@
 aresponses==2.0.0
-coverage==5.0.3
+coverage==5.0.4
 flake8==3.7.9
 flake8-docstrings==1.5.0
 isort==4.3.21