CI: Add tmux version before pytest

Author: tony

.github/workflows/libtmux-ci.yml

@@ -50,6 +50,7 @@ jobs:
         pipenv run flake8
     - name: Test with pytest
       run: |
+        tmux -V
         pipenv run py.test --cov=./ --cov-report=xml
     - uses: codecov/codecov-action@v1
       with: