Make tests pass for catching exceptions.

May now use sys.excepthook to catch exceptions
from threaded handlers.

sleekxmpp/xmlstream/xmlstream.py

@@ -682,6 +682,7 @@ class XMLStream(object):
                         Event handlers and the send queue will be threaded
                         regardless of this parameter's value.
         """
+        self._thread_excepthook()
         self.scheduler.process(threaded=True)
 
         def start_thread(name, target):
@@ -954,3 +955,26 @@ class XMLStream(object):
             self.disconnect()
             self.event_queue.put(('quit', None, None))
             return
+
+    def _thread_excepthook(self):
+        """
+        If a threaded event handler raises an exception, there is no way to
+        catch it except with an excepthook. Currently, each thread has its own
+        excepthook, but ideally we could use the main sys.excepthook.
+
+        Modifies threading.Thread to use sys.excepthook when an exception
+        is not caught.
+        """
+        init_old = threading.Thread.__init__
+        def init(self, *args, **kwargs):
+            init_old(self, *args, **kwargs)
+            run_old = self.run
+            def run_with_except_hook(*args, **kw):
+                try:
+                    run_old(*args, **kw)
+                except (KeyboardInterrupt, SystemExit):
+                    raise
+                except:
+                    sys.excepthook(*sys.exc_info())
+            self.run = run_with_except_hook
+        threading.Thread.__init__ = init