The migration of mostly middle-class, often well-educated and skilled refugees from the war in Syria has stirred lots of hostility and conflict in Europe.  So why has an equally large migration of similar people fleeing the police state in Venezuela gone so much more smoothly across Latin America?  Could it be because Europeans cling to tribal identities while Latin Americans see themselves as a single community?   Demetrios Papademetriou of the Migration Policy Institute explains.