A politician who survived being shot 16 times in an apparent assassination attempt will challenge Tanzania's president in October elections, his party said as rights groups voiced concern about increasing repression ahead of the polls. Tundu Lissu, who clinched the nomination for the leading opposition Chama cha Demokrasia na Maendeleo (CHADEMA) party, is a fierce critic of President John Magufuli. Lissu survived the attempt on his life in 2017 and left to seek medical treatment abroad, returning from exile last week. His attackers have never been found. Magufuli condemned the attack. Lissu's endorsement by all delegates present after prevailing over…