Sign of the Lion (1962)

Pierre Wesselrin is a 40-year-old American who lives in Paris by sponging off his working friends and various wealthy acquaintances. He receives a telegram saying that a rich aunt has died, so he throws a party, using borrowed money of course, and invites all his friends. After discovering that his aunt disinherited him, his luggage is impounded and he is thrown out of his apartment. All his friends are now away for the summer, or are working outside Paris, so he is forced to wander the streets and become a clochard.