France’s most popular television series set in Marseille, France features the country’s ethnic diversity. The nightly soap opera, “Plus Belle la Vie,” that is watched by nearly a fifth of the French population. Some 13 million people tune in at least once a week to follow the fates of various families in the multicultural confusion of Marseille, France’s second largest city. It features a number of families, including the Nassri family from Algeria. “Plus Belle la Vie,” which translates roughly as “Life Is So Sweet,” has shaken French evening television, which has traditionally been built around the 8 p.m. news on each channel, sometimes referred to as France’s Grand Mass. Despite conflicting with the main national newscasts, the soap has lost less than 2 percent of audience share.