Use tox<4.0 due to breaking changes for github workflow

.github/workflows/pythonpackage.yml

@@ -31,6 +31,6 @@ jobs:
         run: |
           sudo apt-get -y update
           sudo apt-get -y install build-essential netbase
-          pip install tox
+          pip install "tox<4.0"
       - name: Run Tox
         run: tox -e py3,functional-py3