Handle the case where there is not an hardware manager service installed.

shell/view/hardwaremanager.py

@@ -14,6 +14,8 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 
+import logging
+
 import dbus
 
 HARDWARE_MANAGER_INTERFACE = 'org.laptop.HardwareManager'
@@ -25,18 +27,31 @@ class HardwareManager(object):
     B_AND_W_MODE = 1
 
     def __init__(self):
-        bus = dbus.SystemBus()
-        proxy = bus.get_object(HARDWARE_MANAGER_SERVICE,
-                               HARDWARE_MANAGER_OBJECT_PATH)
-        self._service = dbus.Interface(proxy, HARDWARE_MANAGER_INTERFACE)
+        try:
+            bus = dbus.SystemBus()
+            proxy = bus.get_object(HARDWARE_MANAGER_SERVICE,
+                                   HARDWARE_MANAGER_OBJECT_PATH)
+            self._service = dbus.Interface(proxy, HARDWARE_MANAGER_INTERFACE)
+        except dbus.DBusException:
+            self._service = None
+            logging.error('Hardware manager service not found.')
 
     def set_display_mode(self, mode):
+        if not self._service:
+            logging.error('Cannot set display mode. Service not found.')
+
         self._service.set_mode(mode)
 
     def set_display_brightness(self, level):
+        if not self._service:
+            logging.error('Cannot set display brightness. Service not found.')
+
         self._service.set_display_brightness(level)
 
     def toggle_keyboard_brightness(self):
+        if not self._service:
+            logging.error('Cannot set keyboard brightness. Service not found.')
+
         if self._service.get_keyboard_brightness():
             self._service.set_keyboard_brightness(False)
         else: