Use html safe IDs for sequences and videos

common/lib/keystore/__init__.py

@@ -113,6 +113,12 @@ class Location(object):
             url += "/" + self.revision
         return url
 
+    def html_id(self):
+        """
+        Return a string with a version of the location that is safe for use in html id attributes
+        """
+        return "-".join(str(v) for v in self.list() if v is not None)
+
     def list(self):
         """
         Return a list representing this location

common/lib/xmodule/seq_module.py

@@ -67,7 +67,7 @@ class SequenceModule(XModule):
         # of script, even if it occurs mid-string. Do this after json.dumps()ing
         # so that we can be sure of the quotations being used
         params = {'items': json.dumps(contents).replace('</script>', '<"+"/script>'),
-                  'element_id': "-".join(str(v) for v in self.location.list()),
+                  'element_id': self.location.html_id(),
                   'item_id': self.id,
                   'position': self.position,
                   'tag': self.location.category}

common/lib/xmodule/video_module.py

@@ -46,7 +46,7 @@ class VideoModule(XModule):
     def get_html(self):
         return self.system.render_template('video.html', {
             'streams': self.video_list(),
-            'id': self.id,
+            'id': self.location.html_id(),
             'position': self.position,
             'name': self.name,
             'annotations': self.annotations,