Reformat rust code with rustfmt 1.0
diff --git a/lib/rs/src/lib.rs b/lib/rs/src/lib.rs
index 7ebb10c..ca5c7d6 100644
--- a/lib/rs/src/lib.rs
+++ b/lib/rs/src/lib.rs
@@ -63,13 +63,11 @@
 /// return the value contained in the result, i.e. `expr.unwrap()`.
 #[cfg(test)]
 macro_rules! assert_success {
-    ($e: expr) => {
-        {
-            let res = $e;
-            assert!(res.is_ok());
-            res.unwrap()
-        }
-    }
+    ($e: expr) => {{
+        let res = $e;
+        assert!(res.is_ok());
+        res.unwrap()
+    }};
 }
 
 pub mod protocol;