Replace pipenv with poetry

.github/workflows/pytest.yaml

@@ -7,32 +7,34 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: [3.6, 3.7, 3.8, 3.9]
+        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 pipenv flake8 wheel
-      - id: cache-pipenv
+      - name: Install Poetry
+        uses: snok/install-poetry@v1
+      - id: cache-poetry
         uses: actions/cache@v1
         with:
-          path: ~/.local/share/virtualenvs
-          key: ${{ runner.os }}-pipenv-${{ hashFiles('**/Pipfile.lock') }}
+          path: ~/.local
+          key: ${{ runner.os }}-python-${{ matrix.python-version }}-poetry-${{ hashFiles('**/poetry.lock') }}
+
+      #----------------------------------------------
+      # install dependencies if cache does not exist
+      #----------------------------------------------
       - name: Install dependencies
-        if: steps.cache-pipenv.outputs.cache-hit != 'true'
-        run: |
-          pipenv install --deploy --dev
+        run: poetry install --no-interaction --no-root
+
       - name: Test with pytest
         run: |
-          pipenv run pytest -svvv
-      - name: Lint with flake8
+          poetry run pytest -svvv
+
+      - name: Code formatting with black
         run: |
-          # stop the build if there are Python syntax errors or undefined names
-          flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics
-          # exit-zero treats all errors as warnings. The GitHub editor is 127 chars wide
-          flake8 . --count --exit-zero --max-complexity=10 --max-line-length=127 --statistics
+          # run black in check mode
+          # if files are not formatted correctly, the build will not go through
+          poetry run black . --check --verbose