Don't rely on dbus importing the exceptions module - import it explicitly.

Also divide up imports in a PEP8-compliant way.

sugar/presence/presenceservice.py

@@ -16,9 +16,13 @@
 # Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 # Boston, MA 02111-1307, USA.
 
-import dbus, dbus.glib, gobject
 import logging
 
+import dbus
+import dbus.exceptions
+import dbus.glib
+import gobject
+
 # XXX use absolute imports
 #   from sugar.presence import buddy, activity
 # this *kind* of relative import is deprecated