In diplomacy, as in politics, there are plenty of cases in which a world leader has been caught unaware on a “hot’’ microphone. There have been fewer, if any, in which that leader has been caught calling another an outright liar. French President Nicolas Sarkozy takes the prize. Sarkozy, in Cannes for the G-20 summit last week, believed he was speaking privately with President Obama when he reportedly described how frustrating he finds Israeli Prime Minister Benjamin Netanyahu.