Welcome back to our queer film retrospective, “A Gay Old Time.” In this week’s column, we’re following that yellow-brick road back to Oz with the 1978 cult-classic musical The Wiz.After waiting for more than 20 years, this weekend finally sees the release of (the first part of) the film adaptation of Wicked. The Broadway show has become a worldwide phenomenon since it first opened in 2003, and the big-screen version promises to be just as massive. However, Wicked is hardly the first property to reinvent and expand the world of Oz.This week we’ll take it back to 1978’s The Wiz, another movie musical adapted from the stage that put its own distinctive spin on the beloved characters and story.