Add black to tox.ini and pyproject.toml

And update docs accordingly

docs/contributing.md

@@ -39,10 +39,10 @@ Documentation should be written in Markdown whenever possible.
 When making changes please keep the following in mind:
 
 * Keep pull requests limited to a single issue
+* Code must be formatted to [Black](https://black.readthedocs.io/en/stable/index.html) standards
+  * Run `tox -e format` to reformat code accordingly
 * Run `tox` to execute style and lint checks
-* Use [Google styling](https://github.com/google/styleguide/blob/gh-pages/pyguide.md) for docstrings
 * When adding new clouds please add detailed documentation under the `docs` directory and code examples under `examples`
-* 4 spaces, no tabs
 
 ## Submit a Merge Request
 

pyproject.toml

@@ -0,0 +1,3 @@
+[tool.black]
+line-length = 79
+target-version = ['py36']

tox.ini

@@ -1,5 +1,6 @@
 [tox]
-envlist = flake8, pylint, pytest, docs
+# As it may be undesired to make formatting changes, by default only check
+envlist = flake8, pylint, pytest, black, docs
 skipsdist = true
 
 [common]
@@ -8,6 +9,7 @@ deps =
     flake8==4.0.1
     flake8-docstrings==1.6.0
     pylint==2.12.2
+    black==21.12b0
     -rrequirements.txt
     -rtest-requirements.txt
 
@@ -26,6 +28,17 @@ envdir = {[common]envdir}
 deps = {[common]deps}
 commands = {envpython} -m flake8 pycloudlib examples setup.py
 
+[testenv:black]
+envdir = {[common]envdir}
+deps = {[common]deps}
+commands = {envpython} -m black . --check
+
+[testenv:format]
+# Should also include isort in the future
+envdir = {[common]envdir}
+deps = {[common]deps}
+commands = {envpython} -m black .
+
 [testenv:docs]
 # Docs uses a separate environment because the changedir will
 # cause tox to recreate the environment.