Bump black from 19.10b0 to 20.8b1 (#72)

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-preview[bot] <support@dependabot.com>

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

requirements-dev.txt

@@ -6,8 +6,8 @@
 #
 appdirs==1.4.4            # via black, virtualenv
 astroid==2.4.2            # via pylint
-attrs==19.3.0             # via black, pytest
-black==19.10b0            # via -r requirements-dev.in
+attrs==19.3.0             # via pytest
+black==20.8b1             # via -r requirements-dev.in
 bleach==3.1.5             # via readme-renderer
 certifi==2020.6.20        # via requests
 cffi==1.14.0              # via cryptography
@@ -25,7 +25,7 @@ keyring==21.2.1           # via twine
 lazy-object-proxy==1.4.3  # via astroid
 mccabe==0.6.1             # via flake8, pylint
 more-itertools==8.4.0     # via pytest
-mypy-extensions==0.4.3    # via mypy
+mypy-extensions==0.4.3    # via black, mypy
 mypy==0.790               # via -r requirements-dev.in
 packaging==20.4           # via bleach, pytest, tox
 pathspec==0.8.0           # via black
@@ -51,7 +51,7 @@ tox==3.15.2               # via -r requirements-dev.in
 tqdm==4.50.1              # via -r requirements.txt, twine
 twine==3.1.1              # via -r requirements-dev.in
 typed-ast==1.4.1          # via black, mypy
-typing-extensions==3.7.4.2  # via mypy
+typing-extensions==3.7.4.2  # via black, mypy
 urllib3==1.25.9           # via requests
 virtualenv==20.0.24       # via tox
 wcwidth==0.2.4            # via pytest