Remove dependency to tox for build-test target

Author: cderici

.github/workflows/test.yaml

@@ -39,8 +39,6 @@ jobs:
         uses: actions/setup-python@v4
         with:
           python-version: ${{ matrix.python }}
-      - name: Install dependencies
-        run: pip install tox
       - name: Run build test target
         run: |
           make build-test

Makefile

@@ -41,13 +41,13 @@ docs:
 	tox -e docs
 
 .PHONY: build-test
-build-test: .tox
+build-test:
 	rm -rf venv
-	$(PY) -m venv venv
+	python3 -m venv venv
 	. venv/bin/activate
-	$(PY) setup.py sdist
+	python3 setup.py sdist
 	pip install ./dist/juju-${VERSION}.tar.gz
-	$(PY) -c "from juju.controller import Controller"
+	python3 -c "from juju.controller import Controller"
 	rm ./dist/juju-${VERSION}.tar.gz
 
 .PHONY: release