Make assert! debuggable

src/lib.rs

@@ -495,7 +495,8 @@ mod test {
         assert_eq!(rx.iter().take(test_tasks).fold(0, |a, b| a + b), test_tasks);
         // `iter().take(test_tasks).fold` may be faster than the last thread finishing itself, so
         // values of 0 or 1 are ok.
-        assert!(pool.active_count() <= 1);
+        let atomic_active_count = pool.active_count();
+        assert!(atomic_active_count <= 1, "atomic_active_count: {}", atomic_active_count);
     }
 
     #[test]