Migrants shout in front of the UNHCR headquarters in Tunisia after police tore a camp apart on April 11. Migrants have been the target of attacks and arrests since February.FETHI BELAID/AFP/Getty Images Police firing tear gas have forcibly cleared camps of African refugees and migrants outside United Nations offices in Tunisia, arresting dozens of people in the latest crackdown in a campaign that has sparked alarm across Africa. Authorities removed the tents, blankets, sleeping bags and cooking equipment that the migrants had been using for the past six weeks while they sheltered outside UN offices after an eruption of anti-foreigner...