Fix exception pollution in retryable()

lib/retry.mjs

@@ -86,9 +86,20 @@ export const exclusive = (func, cooldown = 2000) =>
         }
         else
         {
-            pending = pending
-                .then(() => sleep(cooldown))
-                .then(() => func(...args));
+            pending = (async () =>
+            {
+                try
+                {
+                    await pending;
+                }
+                catch
+                {
+                    // Ignore errors from previous executions
+                }
+
+                await sleep(cooldown);
+                return func(...args);
+            })();
         }
 
         return pending;