Fix Python3 incompatible import path.
Fix Python3 incompatible import path.

mrpau/kolibri,learningequality/kolibri,learningequality/kolibri,indirectlylit/kolibri,lyw07/kolibri,DXCanas/kolibri,benjaoming/kolibri,learningequality/kolibri,lyw07/kolibri,DXCanas/kolibri,DXCanas/kolibri,lyw07/kolibri,mrpau/kolibri,lyw07/kolibri,learningequality/kolibri,mrpau/kolibri,indirectlylit/kolibri,benjaoming/kolibri,benjaoming/kolibri,DXCanas/kolibri,mrpau/kolibri,indirectlylit/kolibri,benjaoming/kolibri,indirectlylit/kolibri