[1.5.x] Fixed #20722 -- Fixed MemcachedCache backend get_many on Python 3.
[1.5.x] Fixed #20722 -- Fixed MemcachedCache backend get_many on Python 3.

Backport of 3c736207a3 from master

ccn-2m/django,imtapps/django-imt-fork,bliti/django-nonrel-1.5,bliti/django-nonrel-1.5,alx-eu/django,ccn-2m/django,ccn-2m/django,bliti/django-nonrel-1.5,imtapps/django-imt-fork,ccn-2m/django,hasadna/django,alx-eu/django,hasadna/django,imtapps/django-imt-fork,alx-eu/django,alx-eu/django,hasadna/django