PHILIP PULLELLA  POPE Francis has paid tribute to an Italian priest killed by an immigrant suffering from mental illness, while far-right politician Matteo Salvini called for a "vendetta". Father Roberto Malgesini, 51, who cared for immigrants and other needy people in the northern city of Como, was found dead from a stab wound outside his residence on Tuesday morning. A Tunisian immigrant who police said was mentally ill later turned himself in to authorities. Speaking at the end of his weekly general audience, Francis said Malgesini was killed "by a needy person who he himself was helping, a person who…