def verify_role!(node, role)
      current_role = node.info['role']
      if current_role.to_sym != role
        raise InvalidNodeRoleError.new(address_for(node), role, current_role)
      end
      role
    end
def verify_role!(node, role)
      current_role = node.info['role']
      if current_role.to_sym != role
        raise InvalidNodeRoleError.new(address_for(node), role, current_role)
      end
      role
    end
Verifies the actual role for a redis node.

 @param [Redis] node the redis node to check
 @param [Symbol] role the role to verify
 @return [Symbol] the verified role
 @raise [InvalidNodeRoleError] if the role is invalid