GABORONE, Botswana (AP) — Festus Mogae, Botswana’s former president who made a national priority of the fight against HIV and AIDS during his tenure from 1998 to 2008, has died at the age of 86, the government said Friday. No cause of death was given. Botswana President Duma Boko said that under Mogae’s leadership, the country earned international respect for principled, sound economic management and a commitment to democracy. He said the country would undergo three days of national mourning in honor of its former head of state. Botswana, a sparsely populated and arid country in southern Africa, is the biggest producer of diamonds by value and the second biggest by volume behind Russia. Diamonds account for around 80% of Botswana’s exports and a quarter of its gross domestic product, according to the International Monetary Fund.…