def constraint_equal?(region, constraint) 
      [region, constraint].collect{ |v| v.nil? || v == '' ? 'us-east-1' : v }.reduce(:==)
    end
def constraint_equal?(region, constraint) 
      [region, constraint].collect{ |v| v.nil? || v == '' ? 'us-east-1' : v }.reduce(:==)
    end
US default constraint is often represented as '' or nil