Christopher Lydon, former host of WGBH’s “The Ten O’Clock News” and WBUR’s “The Connection,” will return to WGBH as a contributor to the “Open Mic” segment of Boston Public Radio. Lydon confirmed to us Wednesday that he was asked to appear on the program by hosts (and friends) Jim Braude and Margery Eagan. Asked what he’d talk about on air, Lydon told us all about his recent trip to Key West, Fla., where he visited Ernest Hemingway’s home, and his obsession with Tennessee Williams ever since seeing “The Glass Menagerie” at the American Repertory Theater. “These two guys are just tangled in my head right now,” Lydon said of the writers. Other contributors to the “Open Mic” segment include Rev. Eugene F. Rivers and new Boston Globe editor Brian McGrory.