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from django.apps import apps as django_apps
from django.core.exceptions import ImproperlyConfigured

from . import settings


def get_site_model():
    """
    Returns the ``Site`` model that is active in this Django project.
    """
    site_model_name = getattr(settings, 'MULTITIER_SITE_MODEL')
    if site_model_name:
        try:
            return django_apps.get_model(site_model_name)
        except ValueError:
            raise ImproperlyConfigured("MULTITIER_SITE_MODEL must be "\
                "of the form 'app_label.model_name'")
        except LookupError:
            raise ImproperlyConfigured("MULTITIER_SITE_MODEL refers to model"\
                " '%s' that has not been installed"
                % settings.MULTITIER_SITE_MODEL)

    return django_apps.get_model('multitier.Site')
