Support unicode in text field.

Part of STUD-868

common/lib/xmodule/xmodule/poll_module.py

@@ -182,13 +182,13 @@ class PollDescriptor(PollFields, MakoModuleDescriptor, XmlDescriptor):
 
     def definition_to_xml(self, resource_fs):
         """Return an xml element representing to this definition."""
-        poll_str = '<{tag_name}>{text}</{tag_name}>'.format(
+        poll_str = u'<{tag_name}>{text}</{tag_name}>'.format(
             tag_name=self._tag_name, text=self.question)
         xml_object = etree.fromstring(poll_str)
         xml_object.set('display_name', self.display_name)
 
         def add_child(xml_obj, answer):
-            child_str = '<{tag_name} id="{id}">{text}</{tag_name}>'.format(
+            child_str = u'<{tag_name} id="{id}">{text}</{tag_name}>'.format(
                 tag_name=self._child_tag_name, id=answer['id'],
                 text=answer['text'])
             child_node = etree.fromstring(child_str)

common/test/data/toy/chapter/poll_test.xml

 <sequential>
 	<poll_question name="T1_changemind_poll_foo" display_name="Change your answer" reset="false">
-        <p>Have you changed your mind?</p>
+        <p>Have you changed your mind? ’</p>
         <answer id="yes">Yes</answer>
         <answer id="no">No</answer>
     </poll_question>