ddl notifier: allow another error in CI assert (#59503)

close #59501

Author: lance6716

pkg/ddl/notifier/subscribe.go

@@ -162,7 +162,9 @@ func (n *DDLNotifier) start() {
 		case <-ticker.C:
 			if err := n.processEvents(ctx); err != nil {
 				intest.Assert(
-					errors.ErrorEqual(err, context.Canceled) || strings.Contains(err.Error(), "mock handleTaskOnce error"),
+					errors.ErrorEqual(err, context.Canceled) ||
+						strings.Contains(err.Error(), "mock handleTaskOnce error") ||
+						strings.Contains(err.Error(), "session pool closed"),
 					fmt.Sprintf("error processing events: %v", err),
 				)
 				logutil.Logger(ctx).Error("Error processing events", zap.Error(err))

pkg/statistics/handle/ddl/ddl.go

@@ -54,7 +54,9 @@ func (h *ddlHandlerImpl) HandleDDLEvent(ctx context.Context, sctx sessionctx.Con
 	err := h.sub.handle(ctx, sctx, s)
 	if err != nil {
 		intest.Assert(
-			errors.ErrorEqual(err, context.Canceled) || strings.Contains(err.Error(), "mock handleTaskOnce error"),
+			errors.ErrorEqual(err, context.Canceled) ||
+				strings.Contains(err.Error(), "mock handleTaskOnce error") ||
+				strings.Contains(err.Error(), "session pool closed"),
 			fmt.Sprintf("handle ddl event failed, err: %v", err),
 		)
 	}