trick to satisfy the CI until #1258 is fixed

examples/mother/lib.rs

@@ -218,6 +218,7 @@ mod mother {
         /// Prints the specified string into node's debug log.
         #[ink(message)]
         pub fn debug_log(&mut self, message: String) {
+            let _ = message;
             ink_env::debug_println!("debug_log: {}", message);
         }
     }