Fix filter use for Python2.
Fix filter use for Python2.

mrpau/kolibri,mrpau/kolibri,mrpau/kolibri,mrpau/kolibri,learningequality/kolibri,indirectlylit/kolibri,indirectlylit/kolibri,indirectlylit/kolibri,learningequality/kolibri,learningequality/kolibri,learningequality/kolibri,indirectlylit/kolibri