Fix venv reference

Author: MDUYN

.github/workflows/test.yml

@@ -102,7 +102,7 @@ jobs:
       #----------------------------------------------
       - name: Run tests
         run: |
-          source .venv/bin/activate
+          source $VENV
           coverage run -m unittest discover -s tests
 #      #----------------------------------------------
 #      #             upload coverage stats