Imports are Python3 compatible

src/plone/app/multilingual/_compat.py

@@ -0,0 +1,9 @@
+# coding=utf-8
+import sys
+
+
+PY3 = sys.version_info[0] == 3
+if PY3:
+    from io import StringIO
+else:
+    from StringIO import StringIO

src/plone/app/multilingual/tests/test_sitemap.py

@@ -1,6 +1,6 @@
 # -*- coding: utf-8 -*-
-from StringIO import StringIO
 from gzip import GzipFile
+from plone.app.multilingual._compat import StringIO
 from plone.app.multilingual.interfaces import IPloneAppMultilingualInstalled
 from plone.app.multilingual.testing import PAM_FUNCTIONAL_TESTING
 from plone.dexterity.utils import createContentInContainer