Run migrations to Rust 2021

src/cache.rs

@@ -329,7 +329,7 @@ mod tests {
         assert_eq!(cache.backing_folder, retrieved_cache.backing_folder);
         let test = cache.has_same_observable_content_as(&retrieved_cache).await;
         println!("Equal? {:?}", test);
-        assert!(test.unwrap(), true);
+        assert!(test.unwrap(), "{}", true);
     }
 
     #[tokio::test]