refactor(test_backends): change import to improve readability
refactor(test_backends): change import to improve readability

replace
from django_cas_ng.backends import CASBackend
by
from django_cas_ng import backends

IRI-Research/django-cas-ng,pbaehr/django-cas-ng,11h42/django-cas-ng,wrygiel/django-cas-ng,nitmir/django-cas-ng,11h42/django-cas-ng,mingchen/django-cas-ng,bgroff/django-cas-ng