'Memcache keys can\'t have spaces in them, so we\'ll remove them from the
DN for maximum compatibility.'

def _cache_key(self, attr_name):

    dn = self._ldap_user.dn.replace('    ', '%20')
    key = (u'auth_ldap.%s.%s.%s' % (self.__class__.__name__, attr_name, dn))
    return key
