France doesn't officially require an IDP for driving, what France instead does require is a French language version of the licence.
For those visiting from Canada, you'll likely find that your driver's licence is already written in both English and French. Some of our recent clientele have not required an additional permit when renting a vehicle.
However, our American clients would certainly be recommended an IDP for any visit in which they plan on renting a vehicle.
In general, better safe than sorry - if your trip plans rely at all on the success of renting a vehicle it will be far, far less stress to get the permit before departing rather than having any sort of pointless argument with the poor staff at your rental car desk.
Remember, just like airlines denying your boarding for a soon-to-expire passport, individual rental car companies may have different standards or requirements when it comes to handing over the keys.