Unlikely that Article 79 is true impossibility standards, but nothing explicit in 79 or 7 to answer the question
Likely commercial impracticability or something like that
The impediment must be beyond the control of the affected party
That the affected party could not reasonably have been expected to take the impediment into account at the time of entry into the contract (i.e. that the impediment was reasonably unforeseeable); AND
That the affected party could not reasonably have been expected to avoid or overcome the impediment or its consequences once the event arises
Do we just say, ok, everything ends here and you bear whatever burden is on your shoulders at that moment.
Do you bring parties back to where they were before contract was entered into? Is this possible??
Do you bring parties to where they would be had everything gone according to the contract?
Affected party is not liable for its failure to perform, but the other party is still entitled to exercise remedies other than a damage claim (and presumably a demand for specific performance)