The story of why Richard Pryor didn’t play the role of Black Bart in “Blazing Saddles” (1974) has been rendered shopworn through many retellings, but it bears mentioning on the occasion of the film’s 50th anniversary. Notwithstanding his role as a scriptwriter for the film, Pryor was deemed by Warner Brothers as too volatile a risk: His drug use and erratic behavior made him uninsurable. Director Mel Brooks begged the front office for Pryor’s inclusion, but to no avail: A stage and television actor, Cleavon Little, took on the role.