Frontends: management of unlaunched SàT Backend (information message and exit)

DBus Bridge Frontend: added an exception to manage unlaunched SàT Backend (BridgeExceptionNoService)
Quick App, jp: a message is print when the previous exception is launched

frontends/quick_frontend/quick_app.py

@@ -21,7 +21,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 from logging import debug, info, error
 from tools.jid  import JID
-from sat_bridge_frontend.DBus import DBusBridgeFrontend
+from sat_bridge_frontend.DBus import DBusBridgeFrontend,BridgeExceptionNoService
 from optparse import OptionParser
 import pdb
 
@@ -38,7 +38,12 @@ class QuickApp():
         self.check_options()
         
         ## bridge ##
-        self.bridge=DBusBridgeFrontend()
+        try:
+            self.bridge=DBusBridgeFrontend()
+        except BridgeExceptionNoService:
+            print(_(u"Can't connect to SàT backend, are you sure it's launched ?"))
+            import sys
+            sys.exit(1)
         self.bridge.register("connected", self.connected)
         self.bridge.register("disconnected", self.disconnected)
         self.bridge.register("newContact", self.newContact)