redirects to correct hostname if requested hostname and settings.CORRECT_HOST does not match

redirect_correct_hostname_middleware.py

from django.http import HttpResponsePermanentRedirect
from django.conf import settings

class RedirectCorrectHostname(object):
    """
    redirects to correct hostname if requested hostname and settings.CORRECT_HOST does not match
    (at heroku domain redirects to custom domain)
    """
    def process_request(self, request):
        if not getattr(settings, 'CORRECT_HOST', None):
            return None
        if request.get_host() == settings.CORRECT_HOST:
            return None

        return HttpResponsePermanentRedirect(
            '{scheme}://{host}{path}'.format(scheme=request.scheme,
                                             host=settings.CORRECT_HOST,
                                             path=request.get_full_path()))