Automatically check the source code formatting using black (#5)

.github/workflows/test.yml

@@ -0,0 +1,34 @@
+# This workflow will install Python dependencies, run tests and lint with a variety of Python versions
+# For more information see: https://help.github.com/actions/language-and-framework-guides/using-python-with-github-actions
+
+name: Python package
+
+on:
+  push:
+    branches: [ $default-branch ]
+  pull_request:
+    branches: [ $default-branch ]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        python-version: [3.7, 3.8, 3.9]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v2
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+          python -m pip install --upgrade pip
+          pip install poetry
+          poetry install
+    - name: Black source code formating check
+      run: |
+        black --check .