Update app.py

app.py

@@ -48,7 +48,7 @@ def main():
         sys.exit(1)   # exit with non-zero status for clarity
     ok, msg = is_endpoint_healthy(uri)
     if not ok:
-        print("Endpoint not ready: {msg}")
+        print(f"Endpoint not ready: {msg}")
         
     #  We want to create a basic GUI calling the ContentAgentUI.. 
     #  The default flow should be to show the "Wake Endpoint" button