skip the extractall test on platforms where os.symlink is not available.

Lib/test/test_tarfile.py

@@ -249,6 +249,7 @@ class MiscReadTest(ReadTest):
         data = open(os.path.join(TEMPDIR, "ustar/symtype"), "rb").read()
         self.assertEqual(md5sum(data), md5_regtype)
 
+    @unittest.skipUnless(hasattr(os,'symlink'), "needs os.symlink")
     def test_extractall(self):
         # Test if extractall() correctly restores directory permissions
         # and times (see issue1735).