Bug 1297460

Description of problem:
error coming out of binding a source ip to different zones is different on fedora 23 than on rhel7. that's probably due to python3.x (see in DEBUG copied to additional info).
additionally, this check is not present in developer testsuite (https://github.com/t-woerner/firewalld/commit/a5965e7c44eb94d5063cf95f89f350f3c28619f0)

Version-Release number of selected component (if applicable):
firewalld-0.3.14.2-4.fc23.noarch

How reproducible:
always

Steps to Reproduce:
use --add-source with same ip on two zones:
firewall-cmd --zone=trusted --add-source=192.168.0.1
firewall-cmd --zone=block --add-source=192.168.0.1

Actual results:
[root@vm-f23 ~]# firewall-cmd --zone=block --add-source=192.168.0.1
Error: not all arguments converted during string formatting
and exitcode: 254 (UNKNOWN_ERROR)

Expected results:
Error: ZONE_CONFLICT
exit code: 18

Additional info:
2016-01-11 15:58:45 DEBUG1: Setting zone of interface 'ens3' to 'FedoraWorkstation'
2016-01-11 15:58:45 DEBUG1: zone.ZoneOfInterfaceChanged('FedoraWorkstation', 'ens3')
2016-01-11 15:58:45 DEBUG1: zone.ZoneChanged('FedoraWorkstation', 'ens3')
2016-01-11 15:58:46 DEBUG1: zone.addSource('trusted', '192.168.0.1')
2016-01-11 15:58:47 DEBUG1: zone.SourceAdded('trusted', '192.168.0.1')
2016-01-11 15:58:49 DEBUG1: zone.addSource('block', '192.168.0.1')
2016-01-11 15:58:49 Traceback (most recent call last):
  File "/usr/lib/python3.4/site-packages/firewall/server/decorators.py", line 57, in dbus_handle_exceptions
    return func(*args, **kwargs)
  File "/usr/lib/python3.4/site-packages/firewall/server/firewalld.py", line 1018, in addSource
    _zone = self.fw.zone.add_source(zone, source, sender)
  File "/usr/lib/python3.4/site-packages/firewall/core/fw_zone.py", line 642, in add_source
    "'%s' already bound to a zone" % source_id)
TypeError: not all arguments converted during string formatting