fail gracefully if system DBus unreachable (#1403)

System bus (DBus) is only required for optional features (non-permanent
connection to jabber server, removable media, etc.), so fail gracefully
(but output errors to logs) if it is unreachable.

This aids testing Sugar inside chroots.

Tested:
- inside chroot (no system bus): errors in log, neighbourhood shows buddies
- on XO-1 (regular session, no NM): no errors, neighbourhood shows buddies, battery shown
- on XO-1 (regular session, NM): no errors, neighbourhood shows buddies and networks, battery shown, disconnecting + automatic reconnect works, shutdown works

Signed-off-by: Sascha Silbe <sascha@silbe.org>

2 files changed, 9 insertions, 8 deletions

diff --git a/src/jarabe/desktop/meshbox.py b/src/jarabe/desktop/meshbox.py
index 76880b8..7b8e3a7 100644
--- a/src/jarabe/desktop/meshbox.py
+++ b/src/jarabe/desktop/meshbox.py
@@ -664,12 +664,13 @@ class DeviceObserver(object):
 class NetworkManagerObserver(object):
     def __init__(self, box):
         self._box = box
-        self._bus = dbus.SystemBus()
+        self._bus = None
         self._devices = {}
         self._netmgr = None
 
     def listen(self):
         try:
+            self._bus = dbus.SystemBus()
             obj = self._bus.get_object(_NM_SERVICE, _NM_PATH)
             self._netmgr = dbus.Interface(obj, _NM_IFACE)
         except dbus.DBusException:
diff --git a/src/jarabe/model/session.py b/src/jarabe/model/session.py
index caf675d..121db28 100644
--- a/src/jarabe/model/session.py
+++ b/src/jarabe/model/session.py
@@ -48,16 +48,16 @@ class SessionManager(session.SessionManager):
         self.initiate_shutdown()
 
     def shutdown_completed(self):
-        bus = dbus.SystemBus()
-        proxy = bus.get_object('org.freedesktop.Hal',
-                               '/org/freedesktop/Hal/devices/computer')
-        pm = dbus.Interface(proxy, \
-                            'org.freedesktop.Hal.Device.SystemPowerManagement')
-
         if env.is_emulator():
             self._close_emulator()
-        else:
+        elif self._logout_mode != self.MODE_LOGOUT:
             try:
+                bus = dbus.SystemBus()
+                proxy = bus.get_object('org.freedesktop.Hal',
+                                       '/org/freedesktop/Hal/devices/computer')
+                pm = dbus.Interface(proxy, \
+                                    'org.freedesktop.Hal.Device.SystemPowerManagement')
+
                 if self._logout_mode == self.MODE_SHUTDOWN:
                     pm.Shutdown()
                 elif self._logout_mode == self.MODE_REBOOT: