[1.6.x] Fixed #21049 -- Fixed autoreload for Python 3
[1.6.x] Fixed #21049 -- Fixed autoreload for Python 3

Changed th system module values check to return a list.
In Python 3 it returns a dict_view which could occassionally produce
a runtime error of "dictionary changed size during iteration".

Backport of 559cb826b8 from master

django-nonrel/django,django-nonrel/django,django-nonrel/django,felixjimenez/django,redhat-openstack/django,felixjimenez/django,dex4er/django,redhat-openstack/django,redhat-openstack/django,felixjimenez/django,dex4er/django,django-nonrel/django,dex4er/django,felixjimenez/django,redhat-openstack/django