Pick of the week: “Begin Again” — It’s not “Once.” It’s not “Sing Street.” But I would argue that John Carney’s second feature, starring Mark Ruffalo as a down-on-his-luck music producer who thinks he’s found a star in singer-songwriter Keira Knightley, does capture the joyful spirit of music and creation. The Cee Lo cameo is ill-advised in retrospect, of course.