Set up and configure Black with current code style

Author: akx

pyproject.toml

@@ -0,0 +1,4 @@
+[tool.black]
+line-length = 99
+target-version = ['py36']
+skip-string-normalization = true

requirements-dev.in

@@ -1,3 +1,4 @@
+black~=21.4b1; platform_python_implementation != "PyPy"
 flake8
 flake8-docstrings
 hacking

requirements-dev.txt

@@ -4,14 +4,19 @@
 #
 #    pip-compile requirements-dev.in
 #
+appdirs==1.4.4
+    # via black
 attrs==20.3.0
     # via pytest
+black==21.4b1 ; platform_python_implementation != "PyPy"
+    # via -r requirements-dev.in
 certifi==2020.12.5
     # via requests
 chardet==4.0.0
     # via requests
 click==7.1.2
     # via
+    #   black
     #   pip-tools
     #   safety
 dparse==0.5.1
@@ -33,11 +38,15 @@ mccabe==0.6.1
     # via flake8
 mock==4.0.3
     # via -r requirements-dev.in
+mypy-extensions==0.4.3
+    # via black
 packaging==20.9
     # via
     #   dparse
     #   pytest
     #   safety
+pathspec==0.8.1
+    # via black
 pep517==0.10.0
     # via pip-tools
 pip-tools==6.1.0
@@ -58,6 +67,8 @@ pytest==6.2.3
     # via -r requirements-dev.in
 pyyaml==5.4.1
     # via dparse
+regex==2021.4.4
+    # via black
 requests==2.25.1
     # via
     #   responses
@@ -72,6 +83,7 @@ snowballstemmer==2.1.0
     # via pydocstyle
 toml==0.10.2
     # via
+    #   black
     #   dparse
     #   pep517
     #   pytest