Bump black from 19.10b0 to 20.8b1

Bumps [black](https://github.com/psf/black) from 19.10b0 to 20.8b1.
- [Release notes](https://github.com/psf/black/releases)
- [Changelog](https://github.com/psf/black/blob/master/CHANGES.md)
- [Commits](https://github.com/psf/black/commits)

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

requirements-test.txt

@@ -1,5 +1,5 @@
 bandit==1.7.0
-black==19.10b0
+black==20.8b1
 flake8==3.8.4
 isort==5.7.0
 mypy==0.800