I'm not sure I could cope with following such a ridiculous and confining rule.
I'm frankly amazed the French are complying. Assuming they are, that is.
We drove through France (from. Spain), via Somport Tunnel to Calais, at the beginning of the "lock down". We had the "Attestation" form, which I had to hand write, since we had no printer. One form per person, per day.
It did appear to be being Policed, we were stopped at one Police Road Block, and, the forms were asked for and scrutinised, at a subsequent check point we were initially indicated to stop, but, were then waved on without any checking, presumably, because of our UK registration plates.