In Paris they call “The Hangover 3” “A Very Bad Trip 3”. Here are some pictures of Bradley Cooper at the premiere in Paris on Mau 27, 2013.
In French, a “trip” is a reference to drugs rather than a journey. The French title comes from the roofies in the first film, which is a bit of a spoiler and perhaps not the best title for the film since they only discover the roofies near the end and it’s not what the whole film is about. A hangover translates to “une gueule de bois” In French which literally means a wooden face. Perhaps it was too long which is why the film did not use this name in French.
Here is a video:
Update: here are some cast photos from the premiere. The people pictured include Heather Graham, Justin Bartha, Ken Jeong, Bradley Cooper, Zach Galifianakis, director Todd Phillips and Ed Helms.