overrides `urlparse.urljoin` since it removes base url path
        https://docs.python.org/2/library/urlparse.html#urlparse.urljoin

def _join_url(self, base, url, admin_forwarder=False):
        """
        overrides `urlparse.urljoin` since it removes base url path
        https://docs.python.org/2/library/urlparse.html#urlparse.urljoin
        """
        if admin_forwarder:
            return base + url
        else:
            return urljoin(base, url)