Add forgotten variable declaration in except.

src/common/ged.py

@@ -79,7 +79,7 @@ class GlobalEventsDispatcher(object):
         if event_name in self.handlers:
             try:
                 self.handlers[event_name].remove((priority, handler))
-            except ValueError:
+            except ValueError as error:
                 log.warning('''Function (%s) with priority "%s" never registered
                 as handler of event "%s". Couldn\'t remove. Error: %s'''
                                   %(handler, priority, event_name, error))