virtmanager not connecting to server

[Gary Dale <garydale@torfree.net>]

I'm running Jessie/AMD64 connecting to Wheezy/ADM64. The KVM virtual 
machines are on the Wheezy machine, which is a also file & print server 
(CUPS, Samba & NFS).

I'm getting an error "Unable to connect to libvirt. You need to install 
openssh-askpass or similar to connect to this host."

The details go:

You need to install openssh-askpass or similar to connect to this host.
Libvirt URI is: qemu+ssh://garydale@TheLibrarian/system
Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/connection.py", line 1020, 
in _open_thread
    self._backend.open(self._do_creds_password)
  File "/usr/share/virt-manager/virtinst/connection.py", line 158, in open
    open_flags)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 105, in openAuth
    if ret is None:raise libvirtError('virConnectOpenAuth() failed')
libvirtError: Cannot recv data: ssh_askpass: exec(/usr/bin/ssh-askpass): 
No such file or directory
Host key verification failed.: Connection reset by peer

Jessie doesn't seem to have an openssh-askpass, just 
razorqt-openssh-askpass. Installing it didn't fix the problem.

I can start the virtual machines on the server using virsh start 
<domain>, and I have no problems with a password-less ssh connection to 
the server. I can ping the server using its name and the virt-manager 
connection fails even when I use the IP address, so it doesn't seem to 
be a name problem.

I had a similar problem a couple of years ago when I was connecting to a 
Squeeze system from Wheezy, but the fix back then isn't working today.

Also this was working until a few days ago. I was fiddling on the server 
to remove a configuration error that was preventing some package updates 
from installing and preventing the network from starting. At this point 
the server is behaving normally except for the connection problem.

One interesting thing is that ifconfig now returns this:
br0       Link encap:Ethernet  HWaddr 00:24:1d:14:d8:42
          inet addr:192.168.1.14  Bcast:192.168.1.255 Mask:255.255.255.0
          inet6 addr: 2002:c654:a32b:0:224:1dff:fe14:d842/64 Scope:Global
          inet6 addr: fe80::224:1dff:fe14:d842/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8336637 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6181383 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:19201144873 (17.8 GiB)  TX bytes:1751340102 (1.6 GiB)

eth0      Link encap:Ethernet  HWaddr 00:24:1d:14:d8:42
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:14861600 errors:0 dropped:0 overruns:0 frame:0
          TX packets:6179185 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:19784178400 (18.4 GiB)  TX bytes:1748665682 (1.6 GiB)
          Interrupt:41 Base address:0x6000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:12033 errors:0 dropped:0 overruns:0 frame:0
          TX packets:12033 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:1161414 (1.1 MiB)  TX bytes:1161414 (1.1 MiB)

virbr0    Link encap:Ethernet  HWaddr ba:4e:bb:4a:67:2a
          inet addr:192.168.122.1  Bcast:192.168.122.255 Mask:255.255.255.0
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

vnet0     Link encap:Ethernet  HWaddr fe:54:00:e2:4b:f1
          inet6 addr: fe80::fc54:ff:fee2:4bf1/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:79 errors:0 dropped:0 overruns:0 frame:0
          TX packets:115 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:500
          RX bytes:12027 (11.7 KiB)  TX bytes:19483 (19.0 KiB)

whereas it used to only have br0, eth0 and lo. Using virsh edit 
<domain>, I verified that it is using the br0 interface and not the 
virbr0 one.