python-libuser don't depend from libuser

Hello.

1)
Description: Ubuntu 16.04.3 LTS
Release: 16.04

Description: Ubuntu 17.10
Release: 17.10
2)
system-config-samba 1.2.63-0ubuntu6
python-libuser 1:0.60~dfsg-1.2

system-config-samba 1.2.73-0ubuntu6
python-libuser 1:0.62~dfsg-0.1ubuntu2

I came from "https://bugs.launchpad.net/ubuntu/+source/system-config-samba/+bug/1387274".
system-config-samba depends from python-libuser, but python-libuser don't depend from libuser (but libuser1, I don't know, what it means), so when system-config-samba call libuser.admin() and package libuser don't installed (and file /etc/libuser.conf don't exist), system-config-samba throw "SystemError: could not open configuration file '/etc/libuser.conf'" and don't started.

I reproduce it on clear Ubuntu 17.10 and unclear 16.04.3. If package libuser not installed, system-config-samba don't work. If libuser installed, always ok.