This insurance is compulsory in France and the owner is entitled to ask for a proof of purchase when you move in. Although most owners do not ask for it, you will be strongly advised to get one as it covers, amongst others, the following risks : explosion or water damage, damage to the building and other properties belonging to the owner of the accommodation you are renting, damage caused to properties belonging to neighbours and third parties.

Before taking out insurance for you and your family with a company, contact your own household insurance as they may offer interesting solutions.

However, be aware that most of of them do not cover you in case of cancellation. And if you are renting an accommodation abroad, it is sometimes difficult to get full or partial refund of what you have already paid for.
Alternatively, you can also check your credit card policy before paying for your trip and accommodation, as some banks cover you in case of cancellation, lost luggage, plane delay, etc.
Enjoy your stay in France