Correction: No, not essential but someone will eventually treat you like shit because you don't speak french, and it's going to be offensive and feel like overt racism, but it'll happen rarely. </rant>
Not as bad as being in France, even when you just have a connection at the international airport and have to get somewhere it is very common to have people look down on you because you are trying to get their attention in English.
Never had a problem personally. If you're going to France, just learn five words and you're good:
"Excuse-moi, parlez-vous anglais?" ("Excuse me, do you speak English?")
(phonetically that's roughly "ex-cues-eh-mwah, par-lay-voo an-glays" with a little emphasis on the "glays", just say it fast and it'll sound recognizable)
You might get no. Then you say, "Oh... no parlez-vous francais... do you know where xyz thing is... xyz thing... xyz thing... y'know xyz thing..." Eventually they'll get it. The two-second politeness of addressing someone in French has always been enough for me.
