Only catch NameError and TypeError when attempting to subclass an

exception (for compatibility with old versions of Python).

Tools/webchecker/wsgui.py

@@ -22,7 +22,7 @@ VERBOSE = 2
 try:
     class Canceled(Exception):
         "Exception used to cancel run()."
-except:
+except (NameError, TypeError):
     Canceled = __name__ + ".Canceled"