Hi,

after installing network-manager-openconnect there's no VPN tab in the
configuration dialog and so I can't enter the VPN gateway address
anywhere to set up the VPN connection.

I did restart NM via

    sudo systemctl restart NetworkManager

and I did also restart the nm-applet via

    killall nm-applet; nohup nm-applet &

but no luck.

What I do:

* click on the applet
* click on "VPN Connections"
* click on "Add a VPN connection..."
* select "Cisco AnyConnect or openconnect (OpenConnect)" (I can also
  select Juniper, PaloAlto or Pulse - there won't be a VPN tab in either
  case)
* click on "Create..."
* the config dialog is shown
* only "General", "Proxy", "IPv4 Settings", "IPv6 Settings" tabs are shown
  * there's no place I found to enter the VPN gateway
* also whatever I do in that dialog, the "Save" button is always greyed
  out

When I try to a VPN connection by executing `nm-connection-editor`,
after pressing the button "Create..." I see in the console:

    ** (nm-connection-editor:27682): WARNING **: 15:31:07.165: Could not load editor VPN plugin for ?org.freedesktop.NetworkManager.openconnect? (missing plugin file "/usr/lib/x86_64-linux-gnu/NetworkManager/libnm-vpn-plugin-openconnect-editor.so").
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.165: gtk_widget_get_parent: assertion 'GTK_IS_WIDGET (widget)' failed
    (nm-connection-editor:27682): GLib-GObject-CRITICAL **: 15:31:07.165: g_object_set_data: assertion 'G_IS_OBJECT (object)' failed
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.165: gtk_notebook_insert_page: assertion 'GTK_IS_WIDGET (child)' failed
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.166: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.167: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
    (nm-connection-editor:27682): libnm-CRITICAL **: 15:31:07.167: ((libnm/nm-vpn-editor.c:49)): assertion '<dropped>' failed
    ** Message: 15:31:07.167: Cannot save connection due to error: Invalid setting VPN: unspecified error
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.167: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
    (nm-connection-editor:27682): libnm-CRITICAL **: 15:31:07.191: ((libnm/nm-vpn-editor.c:49)): assertion '<dropped>' failed
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.191: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
    (nm-connection-editor:27682): libnm-CRITICAL **: 15:31:07.191: ((libnm/nm-vpn-editor.c:49)): assertion '<dropped>' failed
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.191: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed
    (nm-connection-editor:27682): libnm-CRITICAL **: 15:31:07.210: ((libnm/nm-vpn-editor.c:49)): assertion '<dropped>' failed
    (nm-connection-editor:27682): Gtk-CRITICAL **: 15:31:07.210: gtk_widget_set_sensitive: assertion 'GTK_IS_WIDGET (widget)' failed

when I search for
`/usr/lib/x86_64-linux-gnu/NetworkManager/libnm-vpn-plugin-openconnect-editor.so`
I see that it is in the package network-manager-openconnect-gnome.

Since I am running Xfce it is not self-evident that I have
to install a package that says that it is for Gnome.

So I think that it'd be optimal to:

* add a note to the package description saying:
  "you'll probably need the network-manager-openconnect-gnome
  package as well, if you want to manage the connections from
  the GUI"
* maybe add a "Suggests: network-manager-openconnect-gnome"
  to the package?
* and the nm-applet should not fail silently if it doesn't
  find an editor component, but instead it should say so:
  "I could not find the VPN editor component. Did you install
  the network-manager-openconnect-gnome package?"

*t