Bump black from 19.10b0 to 20.8b1 (#164)

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>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

pyproject.toml

@@ -25,7 +25,7 @@ sphinx-rtd-theme = "^0.5.0"
 requests-mock = "^1.8.0"
 docutils = "^0.16"
 pytest = "^6.0.0"
-black = {version = "^19.10b0", allow-prereleases = true}
+black = {version = "^20.8b1", allow-prereleases = true}
 isort = {version = "^5.4.2", allow-prereleases = true}
 flake8 = "^3.8.3"
 mypy = "^0.782"