Noway, the French law is very clear on that one, you can be engaged in a PACS which is a kind of legally relaxed " civil marriage" with a partner female or male whether or not sexually involved looks to be however a private matter and  "marry under the new French Marriage law" another one, the awareness and declaration of a pre existing PACS is not mandatory sealing the case that under the new "Marriage" law you definitely have not a Marriage as commonly understood but a legal contract only.
Which is rather awkward really given that the state is asking its officers to be the official witnesses of a legal contract where one party can contract ignoring the other party is engaged in a similar contract...
I guess the Arcangues Mayor and others are founded to express concerns...
But sure it would be an Euskaraz of a lifetime, guess what a week after after San Fermin.