1) (Backward compatible) Django 1.8 get_current_site RequestSite support
https://github.com/pennersr/django-allauth/commit/1a25ea96efcb969945df53be220bb65d75ef50db
2) simplejson compatibility
try:
    from django.utils import simplejson
except ImportError:
    import json as simplejson
3) try:
    from django.contrib.sites.requests import RequestSite
except ImportError:
# Django < 1.7
from django.contrib.sites.models import RequestSite

4) try:
    from django.apps import apps
    get_model = apps.get_model
except ImportError:
    # Django < 1.7
    from django.db.models import loading
    get_model = loading.get_model
https://github.com/macropin/django-registration/blob/9e27a77f4a47c98cdd404207a983b3831d0781db/registration/compat.py