Add flake8 GitHub Actions Workflow.

Author: domdfcoding

.github/workflows/flake8.yml

@@ -0,0 +1,32 @@
+# This file is managed by 'repo_helper'. Don't edit it directly.
+---
+name: Flake8
+
+on:
+  push:
+  pull_request:
+    branches: ["master"]
+
+jobs:
+  Run:
+    name: "Flake8"
+    runs-on: "ubuntu-18.04"
+
+    steps:
+      - name: Checkout 🛎️
+        uses: "actions/checkout@v2"
+
+      - name: Setup Python 🐍
+        uses: "actions/setup-python@v2"
+        with:
+          python-version: "3.8"
+
+      - name: Install dependencies 🔧
+        run: |
+          python -VV
+          python -m site
+          python -m pip install --upgrade pip setuptools wheel
+          python -m pip install tox
+
+      - name: "Run Flake8"
+        run: "python -m tox -e lint -- --format github"

tox.ini

@@ -76,9 +76,10 @@ deps =
     git+https://github.com/PyCQA/pydocstyle@5118faa7173b0e5bbc230c4adf628758e13605bf
     git+https://github.com/domdfcoding/flake8-quotes.git
     git+https://github.com/domdfcoding/flake8-rst-docstrings.git
-    git+https://github.com/domdfcoding/flake8-rst-docstrings-sphinx.git
+    git+https://github.com/domdfcoding/flake8-rst-docstrings-sphinx.git@v2
+    git+https://github.com/domdfcoding/flake8-github-actions
     pygments>=2.7.1
-commands = python3 -m flake8_rst_docstrings_sphinx domdf_python_tools tests --allow-toolbox
+commands = python3 -m flake8_rst_docstrings_sphinx domdf_python_tools tests --allow-toolbox {posargs}
 
 [testenv:mypy]
 basepython = python3.6