=== modified file 'sessioninstaller/backends/aptd.py'
--- old/sessioninstaller/backends/aptd.py	2012-08-21 06:30:09 +0000
+++ new/sessioninstaller/backends/aptd.py	2012-09-19 12:15:22 +0000
@@ -47,11 +47,18 @@
         if parent:
             dia.realize()
             dia.set_transient_for(parent)
-        dia.run(close_on_finished=True, show_error=True,
-                reply_handler=deferred.callback,
+        dia.run(close_on_finished=True, show_error=False,
+                reply_handler=lambda: True,
                 error_handler=deferred.errback)
+        dia.connect("finished", self._on_finished, deferred, trans)
         return deferred
 
+    def _on_finished(self, diag, deferred, trans):
+        if trans.error:
+            deferred.errback(trans.error)
+        else:
+            deferred.callback()
+
     def _simulate_trans(self, trans, parent, interaction):
         deferred = defer.Deferred()
         trans.simulate(reply_handler=lambda: deferred.callback(trans),