By Nate Raymond and Jonathan Stempel (Reuters) -The U.S. government on Thursday filed a civil lawsuit accusing the drug distributor AmerisourceBergen Corp of contributing to the deadly U.S. opioid epidemic by repeatedly failing to report suspicious orders of prescription painkillers. In a complaint filed in Philadelphia federal court, the Department of Justice said the drug distributor and two units violated their legal obligation to resolve suspicious activity in customer orders, or alert the federal Drug Enforcement Administration (DEA) to suspicious customer behavior. The complaint said Ame…