From 6 January, the French Government extended the list of compelling reasons required to be present, to allow a traveller to enter their country.
French Citizens have always been allowed to travel as in itself, this has been accepted as a compelling reason.
Non-French Citizens are now allowed to travel for business, to France, for reasons linked to the pursuit of an economic activity requiring presence on site, which cannot be postponed (with proof from employer).
You can download the full list of compelling reasons by following the link for those from the UK.
It is also said that travelling through France to reach a property in a third country is to be made easier but no details are available for the moment.