Documentary filmmaker Margaret Brown was born and raised in Mobile, Ala., and has had an absorbing interest in the American South, including her 2004 documentary “Be Here to Love Me: A Film About Townes Van Zandt.” But only while filming “The Order of Myths,” in 2008, she learned of the last known slave ship brought to the United States in the late 1850s, and the nearby community former slaves formed. “I didn't remember learning about that in school. That was the first time I had heard of the Clotilda [ship] or Africatown,” she states. That was the moment when she came across the topic of her newest project, the film “Descendant.” Now, Brown shares how she created partnerships to make the film, and got Questlove, Netflix and the Obamas to become involved in it. But first, Kim Masters banters with Matt Belloni about Warner Bros. Discovery’s unpredictable decision to hire filmmaker James Gunn and producer Peter Safran to run the DC Universe.