automation: install black
This should unblock us from running the code formatting test in
our automated environment.
Differential Revision: https://phab.mercurial-scm.org/D7197
# black pulls in typed-ast, which doesn't install on PyPy.
black ; python_version >= '3.6' and platform_python_implementation != 'PyPy'
# Bazaar doesn't work with Python 3 nor PyPy.
bzr ; python_version <= '2.7' and platform_python_implementation == 'CPython'
docutils
fuzzywuzzy
pyflakes
pygments
pylint
# Needed to avoid warnings from fuzzywuzzy.
python-Levenshtein
# typed-ast dependency doesn't install on PyPy.
typed-ast ; python_version >= '3.0' and platform_python_implementation != 'PyPy'
vcrpy