Added poetry virtualenv caching + wrapped tox and coverage with poetr…

…y to ensure they run in the poetry venv.

.github/workflows/poetry.yml

@@ -42,16 +42,20 @@ jobs:
         uses: Gr1N/setup-poetry@v7
         with:
           poetry-version: 1.1.8
+      - uses: actions/cache@v2
+        with:
+          path: ~/.cache/pypoetry/virtualenvs
+          key: ${{ runner.os }}-poetry-${{ hashFiles('poetry.lock') }}
       - name: Install dependencies
         run: poetry install
       - name: Ensure build successful
         run: poetry build
       - name: Run tox
-        run: tox
+        run: poetry run tox
       - name: Generate coverage reports
         run: >
-          coverage report && coverage xml -o ${{ env.REPORTS_DIR }}/coverage.xml &&
-          coverage html -d ${{ env.REPORTS_DIR }}
+          poetry run coverage report && coverage xml -o ${{ env.REPORTS_DIR }}/coverage.xml &&
+          poetry run coverage html -d ${{ env.REPORTS_DIR }}
       - name: Artifact reports
         if: ${{ ! cancelled() }}
         # see https://github.com/actions/upload-artifact