better network_manager detection

src/gajim.py

@@ -2370,9 +2370,8 @@ class Interface:
 			self.remote_ctrl = None
 
 		if gajim.config.get('networkmanager_support') and dbus_support.supported:
-			try:
 			import network_manager_listener
-			except:
+			if not network_manager_listener.supported:
 				print >> sys.stderr, _('Network Manager support not available')
 
 		self.show_vcard_when_connect = []

src/network_manager_listener.py

@@ -27,23 +27,23 @@ def device_no_longer_active(self, *args):
 		'listen_to_network_manager') and connection.connected > 1:
 			connection._disconnectedReconnCB()
 
+supported = False
 
-from common.dbus_support import system_bus
+try:
+	from common.dbus_support import system_bus
 
-import dbus
-import dbus.glib
+	bus = system_bus.SystemBus()
 
-bus = system_bus.SystemBus()
-
-bus.add_signal_receiver(device_no_longer_active,
+	if 'org.freedesktop.NetworkManager' in bus.list_names():
+		supported = True
+		bus.add_signal_receiver(device_no_longer_active,
 			'DeviceNoLongerActive',
 			'org.freedesktop.NetworkManager',
 			'org.freedesktop.NetworkManager',
 			'/org/freedesktop/NetworkManager')
 
-bus.add_signal_receiver(device_now_active,
+		bus.add_signal_receiver(device_now_active,
 			'DeviceNowActive',
 			'org.freedesktop.NetworkManager',
 			'org.freedesktop.NetworkManager',
 			'/org/freedesktop/NetworkManager')
-