Ric Burns’ four-hour American Masters bio, Andy Warhol: A Documentary Film, is having digital theatrical debuts hosted by pubTV stations that began Sunday in 20 cities around the country, WNET announced. (The late artist’s brother, Paul Warhola, will appear at tomorrow’s screening in the Pittsburgh area, where Warhol grew up.) Emerging Pictures, which seeks to put arthouse films on more screens around the country, is distributing to theaters [15 listed].