Good call. The news story has now come out and that is what they are saying. "White sky trails force France to reveal hypersonic weapon test". Have added the link above.
This seems odd though. They only tell people because it was seen by civilians in two countries? Don't they normally announce these kind of things before the event? And WTF are they doing testing hypersonic weapons above civilians??? Call me crazy but shouldn't they do these kind of tests out at sea?