Use black, enforce with GitHub Actions

.github/workflows/python-formatting.yml

@@ -0,0 +1,28 @@
+name: Python Formatting Check
+
+on:
+  push:
+    branches:
+      - main
+      - master
+  pull_request:
+    branches:
+      - main
+      - master
+
+jobs:
+  formatting:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python 3.8
+      uses: actions/setup-python@v2
+      with:
+        python-version: '3.8'
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        python -m pip install black
+    - name: Run formatting check
+      run: |
+        make ck-format

.gitignore

@@ -2,3 +2,5 @@
 *.diff
 .*.sw*
 /brozzler.egg-info/
+venv
+.idea

Makefile

@@ -0,0 +1,7 @@
+.PHONY: format
+format:
+	venv/bin/black -t py35 -t py36 -t py37 -t py38 -t py39 -t py310 -t py311 -t py312 .
+
+.PHONY: ck-format
+ck-format:
+	venv/bin/black --check .