Fix some minor issues that prevent some tests from being collected.

cms/djangoapps/contentstore/views/tests/test_videos.py

@@ -10,7 +10,6 @@ import re
 from contextlib import contextmanager
 from datetime import datetime
 from functools import wraps
-from StringIO import StringIO
 
 import dateutil.parser
 import ddt
@@ -1417,7 +1416,7 @@ class VideoUrlsCsvTestCase(VideoUploadTestMixin, CourseTestCase):
             response["Content-Disposition"],
             u"attachment; filename={course}_video_urls.csv".format(course=self.course.id.course)
         )
-        response_reader = StringIO(response.content)
+        response_reader = six.StringIO(response.content)
         reader = csv.DictReader(response_reader, dialect=csv.excel)
         self.assertEqual(
             reader.fieldnames,

common/lib/xmodule/xmodule/modulestore/split_mongo/split.py

@@ -61,7 +61,6 @@ import hashlib
 import logging
 from collections import defaultdict
 from importlib import import_module
-from types import NoneType
 
 import six
 from bson.objectid import ObjectId
@@ -2108,7 +2107,7 @@ class SplitMongoModuleStore(SplitBulkWriteMixin, ModuleStoreWriteBase):
         Broke out guts of update_item for short-circuited internal use only
         """
         with self.bulk_operations(course_key):
-            if allow_not_found and isinstance(block_key.id, (LocalId, NoneType)):
+            if allow_not_found and isinstance(block_key.id, (LocalId, type(None))):
                 fields = {}
                 for subfields in six.itervalues(partitioned_fields):
                     fields.update(subfields)