“Rodrigo D: No futuro” explores the bleak and precarious lives of working class street kids in Medellín. So dangerous is this world that three of its nonprofessional actors have been killed violently since production wrapped in 1988. Rodrigo has headaches and thinks about his mother, who died sometime previous to the film’s story. He is also looking for a drum kit so he can start a punk band with his friends, who sell cocaine to school kids, and steal cars to survive.