Kolab on CentOS7 latest upgrade

Hi everybody.

After last upgrade tonight my CentOS7 Kolab server stop to work. There was not 
possible to start wallace (which I must start by hands after each upgrade) and 
kolabd service. After some log reading I found two files: 
 /usr/lib/python2.7/site-packages/pykolab/utils.py and
/usr/lib/python2.7/site-packages/wallace/module_resources.py 
where I must comment the line: from six import string_types

After restart kolabd, wallace, cyrus-imapd seems they work again. Is it a bug? 
I have identical problem at two of my servers. So I stop to upgrade another 
ones.

Greetings, ladas