I have the exact same problem. 
Here is my output when running the program as Till Kamppeter said. 

system-config-printer --debug
Connected as user emil
refresh
Created subscription 7
<monitor.Monitor instance at 0xaa47f8c>: printers and jobs lists provided
update_jobs
Authentication pass: 1
Authentication: password callback set
Authentication pass: 1
Authentication: password callback set
Authentication pass: 1
Authentication: password callback set
get_notifications
update_jobs
Using polkit-1 connection class
+<asyncipp._IPPAuthOperation instance at 0xaa5166c>
New IPPConnection
+<_IPPConnectionThread(Thread-1, initial daemon)>
+<asyncipp.IPPAuthConnection instance at 0xaa515ec>Awaiting further instructions

+<asyncpk1.PK1Connection instance at 0xaa514ec>
+<asyncconn.Connection object at 0xaa515ac>
fetchDevices
Converted ()/{'exclude_schemes': ['dnssd', 'snmp'], 'reply_handler': <bound method _GetDevicesCall._reply_handler of <cupshelpers.cupshelpers._GetDevicesCall object at 0xaa56b6c>>, 'error_handler': <bound method NewPrinterGUI.error_getting_devices of <__main__.NewPrinterGUI instance at 0xaa4746c>>} to (0, [], ['dnssd', 'snmp'])
+_PK1AsyncMethodCall: <asyncpk1._PK1AsyncMethodCall instance at 0xaa56b2c>
Calling PK method DevicesGet
D-Bus call failed: DBusException('The name org.opensuse.CupsPkHelper.Mechanism was not provided by any .service files',)
+<asyncipp._IPPAuthOperation instance at 0xaa56cac>
Next task: (<method 'getDevices' of 'cups.Connection' objects>, (), {'exclude_schemes': ['dnssd', 'snmp']}, <bound method _PK1AsyncMethodCall._ipp_reply_handler of <asyncpk1._PK1AsyncMethodCall instance at 0xaa56b2c>>, <bound method _IPPAuthOperation.error_handler of <asyncipp._IPPAuthOperation instance at 0xaa56cac>>, <bound method _IPPAuthOperation.auth_handler of <asyncipp._IPPAuthOperation instance at 0xaa56cac>>)
-<asyncipp._IPPAuthOperation instance at 0xaa5166c>
Call <method 'getDevices' of 'cups.Connection' objects>
...success
Awaiting further instructions
fetchDevices
Converted ()/{'reply_handler': <bound method _GetDevicesCall._reply_handler of <cupshelpers.cupshelpers._GetDevicesCall object at 0xaa5c04c>>, 'include_schemes': ['dnssd', 'snmp'], 'error_handler': <bound method NewPrinterGUI.error_getting_devices of <__main__.NewPrinterGUI instance at 0xaa4746c>>} to (0, ['dnssd', 'snmp'], [])
+_PK1AsyncMethodCall: <asyncpk1._PK1AsyncMethodCall instance at 0xaa5c0ec>
Calling PK method DevicesGet
D-Bus call failed: DBusException('The name org.opensuse.CupsPkHelper.Mechanism was not provided by any .service files',)
+<asyncipp._IPPAuthOperation instance at 0xaa5c12c>
Next task: (<method 'getDevices' of 'cups.Connection' objects>, (), {'include_schemes': ['dnssd', 'snmp']}, <bound method _PK1AsyncMethodCall._ipp_reply_handler of <asyncpk1._PK1AsyncMethodCall instance at 0xaa5c0ec>>, <bound method _IPPAuthOperation.error_handler of <asyncipp._IPPAuthOperation instance at 0xaa5c12c>>, <bound method _IPPAuthOperation.auth_handler of <asyncipp._IPPAuthOperation instance at 0xaa5c12c>>)
-<asyncipp._IPPAuthOperation instance at 0xaa56cac>
Call <method 'getDevices' of 'cups.Connection' objects>
DESTROY: <asyncpk1._PK1AsyncMethodCall instance at 0xaa56b2c>
-_PK1AsyncMethodCall: <asyncpk1._PK1AsyncMethodCall instance at 0xaa56b2c>
Calling <bound method PrinterFinder._do_find of <probe_printer.PrinterFinder instance at 0xaa56b2c>>
192.168.1.8:9100 OPEN
Device found: socket://192.168.1.8:9100
Can't connect to server/printer
socket: host is 192.168.1.8, port is 9100
192.168.1.8: /usr/lib/cups/backend/snmp "${HOST}"
...success
Awaiting further instructions
fetchPPDs
+<ppdsloader.PPDsLoader instance at 0xaa5c7ac>
Asking PackageKit to install drivers
Failed to talk to PackageKit: org.freedesktop.DBus.Error.ServiceUnknown: The name org.freedesktop.PackageKit was not provided by any .service files
Asking Jockey to install drivers
socket: host is 192.168.1.8, port is 9100
DESTROY: <asyncconn.Connection object at 0xaa515ac>
DESTROY: <asyncpk1.PK1Connection instance at 0xaa514ec>
DESTROY: <asyncipp.IPPAuthConnection instance at 0xaa515ec>
Putting None on the task queue
Next task: None
Thread exiting
-<asyncipp._IPPAuthOperation instance at 0xaa5c12c>
-<asyncconn.Connection object at 0xaa515ac>
DESTROY: <asyncpk1._PK1AsyncMethodCall instance at 0xaa5c0ec>
-<asyncpk1.PK1Connection instance at 0xaa514ec>
-<asyncipp.IPPAuthConnection instance at 0xaa515ec>
-_PK1AsyncMethodCall: <asyncpk1._PK1AsyncMethodCall instance at 0xaa5c0ec>
-<_IPPConnectionThread(Thread-1, stopped daemon -1234211984)>
Device found: hp:/net/Photosmart_2570_series?ip=192.168.1.8
parsed path: fname='smb://192.168.1.8/' server='192.168.1.8' share='' path='' options=''
SMBC_check_options(): server='192.168.1.8' share='' path='' options=''
pysmb: got password callback
pysmb: got password callback
pysmb: operation failed: RuntimeError(13, 'Permission denied')
pysmb: authentication pass: 2
pysmb: try auth as guest
pysmb: got password callback
pysmb: got password callback
pysmb: operation failed: RuntimeError(13, 'Permission denied')
pysmb: authentication pass: 3
pysmb: try as emil
Got Jockey result: dbus.Array([], signature=dbus.Signature('s'))
Asking CUPS for PPDs
Using polkit-1 connection class
+<asyncipp._IPPAuthOperation instance at 0xaa5ca4c>
New IPPConnection
+<_IPPConnectionThread(Thread-3, initial daemon)>
Awaiting further instructions
+<asyncipp.IPPAuthConnection instance at 0xaa5ca0c>
+<asyncpk1.PK1Connection instance at 0xaa5c9ac>
+<asyncconn.Connection object at 0xaa5ca8c>
+_PK1AsyncMethodCall: <asyncpk1._PK1AsyncMethodCall instance at 0xaa5cc6c>
+<asyncipp._IPPAuthOperation instance at 0xaa5cc8c>
Next task: (<method 'getPPDs' of 'cups.Connection' objects>, (), {}, <bound method _PK1AsyncMethodCall._ipp_reply_handler of <asyncpk1._PK1AsyncMethodCall instance at 0xaa5cc6c>>, <bound method _IPPAuthOperation.error_handler of <asyncipp._IPPAuthOperation instance at 0xaa5cc8c>>, <bound method _IPPAuthOperation.auth_handler of <asyncipp._IPPAuthOperation instance at 0xaa5cc8c>>)
-<asyncipp._IPPAuthOperation instance at 0xaa5ca4c>
Call <method 'getPPDs' of 'cups.Connection' objects>
Caught non-fatal exception.  Traceback:
File "/usr/share/system-config-printer/probe_printer.py", line 358, in _probe_smb
    while smbc_auth.perform_authentication () > 0:
File "/usr/share/system-config-printer/probe_printer.py", line 210, in perform_authentication
    return self._do_perform_authentication_result
AttributeError: BackgroundSmbAuthContext instance has no attribute '_do_perform_authentication_result'
Continuing anyway..
Done
...success
Awaiting further instructions
Killed



I hope it is going to help. I am new to testing Ubuntu releases, so I don't know if there is anything else I could do, so that the developers can fix the problem.