Apply and ensure Black formatting

.github/PULL_REQUEST_TEMPLATE.md

@@ -7,3 +7,4 @@ Delete them if they are not appropriate for this pull request.
 - [ ] I have properly documented new or changed features in the documention or in the docstrings
 - [ ] I have properly documented unusual changes to the code in the comments around it
 - [ ] I have made note of any breaking/backwards incompatible changes
+- [ ] I formatted my code using `black -t py36` 

.github/workflows/ci.yml

@@ -0,0 +1,14 @@
+name: Code Format Check
+
+on: [pull_request]
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2    
+      - name: Black Code Formatter
+        uses: lgeiger/[email protected]    
+        with:
+          args: "--check --target-version py36 $GITHUB_WORKSPACE"

CONTRIBUTING.md

@@ -2,9 +2,13 @@
 
 ## Keeping/Improving code quality
 
-- Respect PEP8 standards!
+- Respect PEP8 conventions!
 - Just the right amount of comments. Try to write auto-documented code (with very explicit variable names).
 - If you introduce a new functionality or fix a subtle bug, document it in the docstring/code.
+- Moviepy's team adopted [black](https://github.com/psf/black) to autoformat the code. This is enforced for any pull request. 
+
+> Tip: use `black -t py36 .` to autoformat your code, or set black as a plugin of your editor. 
+
 
 ## Using Github
 
@@ -26,10 +30,11 @@
 - To make a change
   - Create a new local branch: `git checkout -b branchname`
   - Make any changes in it
+  - Make sure that your code still conforms to the formatting standard: `black -t py36 .`
   - Run the test suite over it to expose any problems: `python3 setup.py test`
   - Push the local branch to your fork on github: `git push -u origin branchname`
   - Go to github.com/yourname/moviepy and it will display 'Recently pushed branches' giving you the option to make a Pull Request to the main repo
   - Fill in any details for your PR and submit
   - The test suite will automatically be ran over your submission
   - A moviepy collaborator will review your code, and help you to get it merge-ready
-- You don't have to have finished your feature/bugfix before submitting a PR; just mention that it is a work-in-progress
+- You don't have to have finished your feature/bugfix before submitting a PR; just mention that it is a work-in-progress