fix errors

common/lib/xmodule/xmodule/modulestore/__init__.py

@@ -169,6 +169,7 @@ class BulkOperationsMixin(object):
     def __init__(self, *args, **kwargs):
         super(BulkOperationsMixin, self).__init__(*args, **kwargs)
         self._active_bulk_ops = ActiveBulkThread(self._bulk_ops_record_type)
+        self.signal_handler = None
 
     @contextmanager
     def bulk_operations(self, course_id, emit_signals=True):

common/lib/xmodule/xmodule/util/null_handler.py

+# pylint: disable=missing-docstring
+
 class NullHandler(object):
     """
     Responds to an any method call.
     """
     def __getattr__(self, name):
-        def method(*args, **kwargs):
+        def method(*args, **kwargs): # pylint: disable=unused-argument
             pass
         return method
-