eliminate tox, use pytest without it

Author: chrissimpkins

.github/workflows/python-ci.yml

@@ -20,9 +20,7 @@ jobs:
         run: |
           python -c "import sys; print(sys.version)"
           python -c "import struct; print(struct.calcsize('P') * 8)"
-      - name: Install dependencies
-        run: |
-          python -m pip install --upgrade pip
-          pip install tox
-      - name: Test with tox
-        run: tox -e py39
+      - name: Install testing dependencies and project
+        run: pip install -r -dev-requirements.txt .
+      - name: Run pytest tests
+        run: pytest