invoke the correct python interpreter on rocky

Author: matekelemen

.github/workflows/ci.yml

@@ -376,7 +376,7 @@ jobs:
         export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:${GITHUB_WORKSPACE}/bin
         cd tests
         # TODO delete build dir to make sure the linking etc works correctly? (Needs to be done after running CTests)
-        python3 run_python_tests.py
+        python3.8 run_python_tests.py
 
 
   Ubuntu-minimum-CMake: