Wow! France! You'll be seeing a lot of foie gras on the menu, I can imagine
I've never been over seas so I can't speak from experience in that regard, but I can speak from experiences here in Aus. If I'm ever stuck in a restaurant where every item on the menu has meat, except for the sides, then I order a bunch of sides and ask that they make it a 'main'. In fact, one of my favourite restaurants (in Narellan, NSW) is a German-Czech Restaurant where there are absolutely NO veg*an main options. Every time I go, I order as a main, my favourite sides which are pan-fried potatoes, vegies and crumbed mushrooms and they always give me a huge portion, equivalent to any other main on the menu.
I think you'll find that most restaurants want to make you comfortable and satisfied, though I have been told that the people of France are quite rude, particularly to tourists, lol!
As Callum mentioned, talk to the waiter and see what they can do for you.
Have fun over there, I'm really jealous!