Set time zone from cookie
Edit: Well my previous suggestions don't work with the fact that
get_response has to be called with the correct timezone active.




Is the time_zone attribute from GeoIP2 always compatible with
pytz btw.?


Perhaps the following would work, verifying the cookie value only once
and discarding it if it doesn't fit:

cookie = request.COOKIES.get(TIMEZONE_COOKIE_NAME)
if cookie not in pytz.all_timezones_set:
    cookie = None

if not cookie and request.ip:
    try:
        cookie = GeoIP2().city(request.ip).time_zone
    except GeoIP2Error:
        self.logger.warning('Could not determine time zone of ip address: %s', request.ip)

if cookie:
    timezone.activate(pytz.timezone(cookie))

response = self.get_response(request)
if cookie:
    response.set_cookie(TIMEZONE_COOKIE_NAME, cookie)
return response


So, downside is a lot of mentions of cookie, upside is that it's not
more costly what you had before and the call to set the timezone is only
there once.



Last point, if anything like this happens to be needed more than once,
put it into separate functions.  This snippet is a bit short to make
that call.