AULNAY-SOUS-BOIS, France, Nov. 4 - France's worst urban violence in a decade exploded for a ninth night on Friday as bands of youths roamed the immigrant-heavy, working-class suburbs of Paris, setting fire to dozens of cars and buildings while the government struggled over the violence and the underlying frustrations fueling it. The unrest, which has also spread to other parts of France with large North African and Arab populations, prompted the American and Russian governments to warn citizens visiting Paris to avoid its poor, outlying neighborhoods. France reduced train service to Charles de Gaulle Airport after two trains became targets...