make sure tox is installed in the right place

.github/workflows/ci_test.yml

@@ -116,6 +116,7 @@ jobs:
             python -m pip install --upgrade pip
             python -m pip install tox
         - name: Print Python, pip, and tox versions
+          shell: bash -el {0}
           run: |
             python -c "import sys; print(f'Python {sys.version}')"
             python -c "import pip; print(f'pip {pip.__version__}')"