The Tesla caught on fire during a test drive that included a company representative and two prospective customers. After the three people discovered something was amiss, they pulled the vehicle over and exited it in time before the sedan went up in flames and was fully consumed in about five minutes. After a three-week probe, Tesla found that the electrical connection in question was installed by a human being, as opposed to the robots that usually do the job, hence, the mishap. You just can't trust those humans.
To be fair, it's worth noting that about 150,000 gas-powered vehicles go up in flames in the US every year, so it's not like Tesla is dealing with an epidemic. A similar incident (albeit in far colder climes) happened earlier this year when a Tesla in Norway was destroyed by a fire caused by a short circuit.
Back in 2013, a handful of Teslas got torched because of incidents involving road debris getting kicked up under the car and piercing the vehicle's battery pack, which runs along the car's floor. More recently, Tesla's safety issues have involved people having a little too much faith in the car's Autopilot feature and getting into accidents as a result. So the French fire is a bit of deja vu.