When driving a car or motorbike in France you need to carry your driving license, insurance papers (attestation d’assurance) and carte grise (French log book) on you at all times.
If you get stopped by the police at a random spot check and can’t produce the above documents you will get fined!
In 7 years living in Brittany, I have been pulled up 4 times! Each time, they checked my driving license, insurance papers, Contrôle Technique, tires and asked me if I had had a drink before driving. They never breathalyzed me, I guess I don't look like I am a big drinker!
Random spot checks are frequent especially Saturday night and Sunday afternoon.