In a large cast-iron or other heavy skillet, cook sausage until no longer pink; drain. Remove and keep warm. In the same skillet, saute the onion, green pepper, celery, carrot and garlic in olive oil for until vegetables are tender, 3-4 minutes. Stir in the tomatoes, chickpeas, tomato paste, sugar, Italian seasoning, pepper flakes and sausage. , Bring to a boil. Reduce heat; simmer, uncovered until heated through, 4-6 minutes.