⬆️ Bump black from 19.3b0 to 19.10b0

Bumps [black](https://github.com/psf/black) from 19.3b0 to 19.10b0.
- [Release notes](https://github.com/psf/black/releases)
- [Commits](https://github.com/psf/black/commits)

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

Author: dependabot-preview[bot]

requirements_dev.txt

@@ -1,5 +1,5 @@
 autopep8==1.4.4
-black==19.3b0
+black==19.10b0
 blacken-docs==1.3.0
 pip==19.3.1
 pre-commit==1.20.0