Fundamentally, a buyer can walk away from buying something. There's a contract and it surely has contingencies for these cases, no need for drama.
That said, it does seem like the contract was broken in a really nasty way - apparently the French were told about it mere hours before the media announcement.
So the French are very angry, and possibly over-reacting, but only a little, it seems understandable. It makes sense for them to lash out at EU-wide negotiations with Australia.
But of course that affects countries that had nothing to do with the whole ordeal.
The cynic in me wonders if there is an element of some kind of political point-scoring by the British; Britain is on course to sign a deal with Australia. Some kind of, "see, we can do it and they can't".
Worth keeping in perspective that trade with Australia is a small slice of EU's trade overall.