Place the oil, onions and bacon in a medium pan and cook on medium-high for 10 minutes, stirring occasionally.
Add the tomatoes (or tomato paste) and cook for 5 additional minutes, stirring occasionally.
Add the green beans and salt, and cook for another 8 to 10 minutes (or until the green beans have slightly softened and begin to stick to the pan).
Add 2 cups of water (enough to barely cover the green beans), mustard, parsley stems and sugar. Bring to a gentle boil then lower the heat to medium low, cover and tilt the lid. Braise for 1 to 1 1/2 hours, stirring occasionally.
As the green beans braise, the liquid will evaporate. Be sure to continue to add the remaining 2 cups of water throughout the cooking process. Cook until the liquid is mostly evaporated and the green beans are soft and tender. Add more water if necessary.
Check the green beans after 1 hour. If they have reached the preferred tenderness, add the red wine vinegar and heat through for another 5 minutes. Salt to taste.