virt-manager is unable to open a connection to the libvirt management daemon over ssh (pubkey)

[Alvin]

Binary package hint: virt-manager

Steps to reproduce:
- Verify that public key authentication for <username> works, so that $ ssh virthost logs you in on virthost without asking a password.
- Verify that <user> is in group libvirtd on virthost. (Test by using virt list or something)
- virt-manager: File > Add Connection > QEMU:KVM, Remote tunnel over SSH, Hostname: username@virthost > Connect

Unable to open a connection to the libvirt management daemon.
libvirt URI is: qemu+ssh://username@virthost/system

Verify that:
 - The 'libvirt-bin' package is installed
 - The 'libvirtd' daemon has been started
 - That you have access to '/var/run/libvirt/libvirt-sock'

Details
Unable to open connection to hypervisor URI 'qemu+ssh://username@virthost/system':
server closed connection
Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/connection.py", line 896, in _try_open
    None], flags)
  File "/usr/lib/python2.6/dist-packages/libvirt.py", line 111, in openAuth
    if ret is None:raise libvirtError('virConnectOpenAuth() failed')
libvirtError: server closed connection

Maybe you need to install ssh-askpass in order to authenticate.

Expected:
Because ssh works with public key authentication, virt-manager shouldn't complain and just connect to the server.

ProblemType: Bug
DistroRelease: Ubuntu 10.04
Package: virt-manager 0.8.2-2ubuntu8
ProcVersionSignature: Ubuntu 2.6.32-23.37-generic 2.6.32.15+drm33.5
Uname: Linux 2.6.32-23-generic x86_64
NonfreeKernelModules: nvidia
Architecture: amd64
Date: Wed Jul 7 11:42:55 2010
PackageArchitecture: all
ProcEnviron:
 LANGUAGE=
 PATH=(custom, user)
 LANG=C
 SHELL=/bin/bash
SourcePackage: virt-manager