Add "Darker" github action (#1373)

Adds a pyproject.toml for default black/darker configuration
Adds a "Darker" github action which picks up on black linting issues for the sections of a file which have changed

.github/workflows/darker-pr.yml

@@ -0,0 +1,50 @@
+---
+name: 'Python formatting linter (Darker / Black)'
+
+on:
+  workflow_dispatch:
+  pull_request:
+    branches:
+      - main
+
+permissions:
+  contents: read
+  pull-requests: read
+
+# This allows a subsequently queued workflow run to interrupt previous runs
+concurrency:
+  group: '${{ github.workflow }} @ ${{ github.event.pull_request.head.label || github.head_ref || github.ref }}'
+  cancel-in-progress: true
+
+jobs:
+  check-darker:
+    runs-on: ${{ fromJSON('["ubuntu-latest", "self-hosted"]')[github.repository == 'github/docs-internal'] }}
+    steps:
+      - name: Set up Python
+        uses: actions/setup-python@v3
+        with:
+          python-version: ${{ inputs.python }}
+
+      - name: Checkout
+        uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
+          ref: ${{ github.event.pull_request.head.sha }}
+
+      - name: Install darker
+        shell: bash
+        run: |
+          pip install darker
+
+      - name: Rebase against current base
+        shell: bash
+        run: |
+          git config user.email "[email protected]"
+          git config user.name "Git Hub Testing Rebase"
+          git rebase ${{ github.event.pull_request.base.sha }}
+          git show -s
+
+      - name: Run darker
+        shell: bash
+        run: |
+          darker --check --diff --color --rev ${{ github.event.pull_request.base.sha }}..

pyproject.toml

@@ -0,0 +1,18 @@
+[tool.black]
+skip-string-normalization = false
+line-length = 120
+target-version = ['py37', 'py38']
+extend-exclude = '''
+/(
+  | plugins/module_utils/_version.py
+)/
+'''
+
+[tool.darker]
+revision = "origin/main.."
+
+src = [
+    "plugins",
+    "tests/unit",
+    "tests/integration",
+]