[1.4.x] Fixed #21823 -- Upgraded six to 1.5.2
[1.4.x] Fixed #21823 -- Upgraded six to 1.5.2

Backport of 780ae7e9f8 from master.

riklaunim/django-custom-multisite,riklaunim/django-custom-multisite,riklaunim/django-custom-multisite