Fix double quotes (#553)

ros2_control_demo_testing/ros2_control_demo_testing/test_utils.py

@@ -68,7 +68,7 @@ def check_controllers_running(node, cnames, namespace=""):
  time.sleep(0.1)
  assert all(
  found.values()
- ), f"Controller node(s) not found: {', '.join(["ns: " + namespace_api + ", ctrl:" + cname for cname, is_found in found.items() if not is_found])}, but seeing {node.get_node_names_and_namespaces()}"
+ ), f"Controller node(s) not found: {', '.join(['ns: ' + namespace_api + ', ctrl:' + cname for cname, is_found in found.items() if not is_found])}, but seeing {node.get_node_names_and_namespaces()}"
 
  found = {cname: False for cname in cnames} # Define 'found' as a dictionary
  start = time.time()