Rinse and drain sauerkraut well. In a large saucepan, add beef bullion cubes to 1 cup heated water. Dissolved cubes. Add sauerkraut. Cover and boil for 20 minutes. When sauerkraut is done, reserve juice. Fry bacon; reserve drippings. Add onion and brown. Add flour and thicken. To flour mixture, add sauerkraut juice, stirring constantly. When smooth, add this mixture along with fried bacon to sauerkraut, mix well. Season with pepper to taste. Add slices of cooked kielbasa to mixture and serve.