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>

requirements-dev.txt

@@ -1,7 +1,7 @@
 # Require base requirements first.
 -r requirements.txt
 # Now for the dev specific stuff
-black==19.3b0
+black==19.10b0
 coverage==4.5.4
 coveralls==1.8.2
 flake8==3.7.9