Fix unused function error return value

citadel-tool/src/image/mod.rs

@@ -255,7 +255,7 @@ fn install_image(arg_matches: &ArgMatches) -> Result<(), Box<dyn std::error::Err
     if image_dest.exists() {
         rotate(&image_dest)?;
     }
-    util::rename(source, &image_dest);
+    util::rename(source, &image_dest)?;
     Ok(())
 }