$ virt-manager --debug
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (cli:256) Launched with command line: virt-manager --debug
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (.virt-manager-wrapped:144) virt-manager version: 1.3.1
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (.virt-manager-wrapped:145) virtManager import: <module 'virtManager' from '/nix/store/ipz4vya2hb0z7vls2vr2pf8ixh327kfh-virt-manager-1.3.1/share/virt-manager/virtManager/__init__.pyc'>
** (virt-manager:13819): WARNING **: Error retrieving accessibility bus address: org.freedesktop.DBus.Error.ServiceUnknown: The name org.a11y.Bus was not provided by any .service files
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (.virt-manager-wrapped:204) GTK version: 3.18.5
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (engine:496) libguestfs inspection support: False
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (systray:154) Showing systray: False
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (engine:1028) processing cli command uri= show_window= domain=
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (engine:1030) No cli action requested, launching default window
(virt-manager:13819): dconf-WARNING **: failed to commit changes to dconf: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name ca.desrt.dconf was not provided by any .service files
(virt-manager:13819): dconf-WARNING **: failed to commit changes to dconf: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name ca.desrt.dconf was not provided by any .service files
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (manager:203) Showing manager
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (engine:401) window counter incremented to 1
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (engine:158) No stored URIs found.
[Sun, 20 Dec 2015 15:23:14 virt-manager 13819] DEBUG (engine:140) Initial gtkapplication activated
[Sun, 20 Dec 2015 15:23:15 virt-manager 13819] DEBUG (engine:225) Determining default libvirt URI
[Sun, 20 Dec 2015 15:23:15 virt-manager 13819] DEBUG (packageutils:39) No PackageKit packages to search for.
After adding a new connection via
File -> Add Connection... -> [x] Autoconnect -> Connect, then closing and starting virt-manager again, the previously setup connection(s) is not there.