Exception in GTK frontend when attempting to connect to wifi: no logind support

The following exception occurred when 'Connect' button was clicked after entering the wireless password on 'Wireless' screen on a non-live session installation using saucy desktop with 20130510 image.

Exception in GTK frontend (invoking crash handler):
Traceback (most recent call last):
  File "/usr/lib/ubiquity/ubiquity/frontend/gtk_ui.py", line 1435, in on_next_clicked
    if ui.plugin_on_next_clicked():
  File "/usr/lib/ubiquity/plugins/ubi-wireless.py", line 150, in plugin_on_next_clicked
    self.nmwidget.connect_to_ap()
  File "/usr/lib/ubiquity/ubiquity/nm.py", line 492, in connect_to_ap
    self.view.connect_to_selection(passphrase)
  File "/usr/lib/ubiquity/ubiquity/nm.py", line 412, in connect_to_selection
    self.wifi_model.connect_to_ap(model[parent][0], ssid, passphrase)
  File "/usr/lib/ubiquity/ubiquity/nm.py", line 137, in connect_to_ap
    signature='a{sa{sv}}oo'))
  File "/usr/lib/python3/dist-packages/dbus/proxies.py", line 145, in __call__
    **keywords)
  File "/usr/lib/python3/dist-packages/dbus/connection.py", line 651, in call_blocking
    message, timeout)
dbus.exceptions.DBusException: org.freedesktop.DBus.GLib.UnmappedError.NmManagerError.Code4: Not authorized to control networking.

The steps to reproduce:
1. Boot the hardware with a saucy installation usb
2. Press any key when human-keyboard screen appears
3. Leave the default 'English' language selection and click continue (any attempt to connect to wifi networks at this stage would fail with 'Not authorized to control networking' message)
4. Click 'Continue' on the 'Preparing to install Ubuntu' screen (here the connection status to the internet would not be ticked)
5. Now on the 'Wireless' screen, Enter the password for the known wifi network and click 'Connect'
6. The crash could be observed at this point.

ProblemType: Bug
DistroRelease: Ubuntu 13.10
Package: ubiquity 2.15.1
ProcVersionSignature: Ubuntu 3.9.0-1.5-generic 3.9.1
Uname: Linux 3.9.0-1-generic x86_64
ApportVersion: 2.10-0ubuntu3
Architecture: amd64
CasperVersion: 1.332
Date: Fri May 10 11:17:38 2013
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity initrd=/casper/initrd.lz quiet splash -- apt-setup/restricted=false apt-setup/multiverse=false oem-config/enable=true
LiveMediaBuild: Ubuntu 13.10 "Saucy Salamander" - Alpha amd64 (20130510)
MarkForUpload: True
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)