Fix tests introduced in 34c581a3.

tests.py

@@ -813,9 +813,14 @@ class TestYara(unittest.TestCase):
         r = yara.compile(source='rule test { condition: ext_str matches /ssi$/ }', externals={'ext_str': 'mississippi'})
         self.assertFalse(r.match(data='dummy'))
 
-        self.assertRaises(UnicodeEncodeError, yara.compile,
-            source="rule test { condition: true}",
-            externals={'foo': u'\u6765\u6613\u7f51\u7edc\u79d1' })
+        if sys.version_info[0] >= 3:
+            self.assertTrue(yara.compile(
+                source="rule test { condition: true}",
+                externals={'foo': u'\u6765\u6613\u7f51\u7edc\u79d1' }))
+        else:
+            self.assertRaises(UnicodeEncodeError, yara.compile,
+                source="rule test { condition: true}",
+                externals={'foo': u'\u6765\u6613\u7f51\u7edc\u79d1' })
 
     def testCallbackAll(self):
         global rule_data