use Error explicitly

src/scope.rs

@@ -247,7 +247,7 @@ where
 
     /// Registers middleware, in the form of a closure, that runs during inbound
     /// processing in the request lifecycle (request -> response), modifying
-    /// request as necessary, across all requests managed by the *Scope*.  
+    /// request as necessary, across all requests managed by the *Scope*.
     /// Scope-level middleware is more limited in what it can modify, relative
     /// to Route or Application level middleware, in that Scope-level middleware
     /// can not modify ServiceResponse.