test__socket_dns.py: add test case for international domain name

greentest/test__socket_dns.py

 #!/usr/bin/python
+# -*- coding: utf-8 -*-
 import sys
 import re
 import greentest
@@ -150,5 +151,11 @@ class TestRemote(TestCase):
         self._test('sdfsdfgu5e66098032453245wfdggd.com')
 
 
+class TestInternational(TestCase):
+
+    def test(self):
+        self._test(u'президент.рф')
+
+
 if __name__ == '__main__':
     greentest.main()