Gay Divorce by Cole Porter. It had a "The" added at the start of the movie title, too! (And an acute accent in there as well, if we're going to get fussy.) Otherwise known to the production code as "There's nothing funny about divorce, but if it's already happened, no harm in having a good time."
Staying on the subject of this same musical, a 3-parter:
(1) The stage show and the movie both have full musical scores, with only one song in common. What is its title?
(2) Which song from the movie won an Academy Award?
(3) What special place in Oscar history does that award have?