event: don't catch systemexit from handler execution

This means that anyone firing an event can get a systemexit and result in
their process exiting, which isn't ideal, but behaves the way it used to (in
particular, ensures that a sanity check failure will halt the build). This
should be revisited in the future.

(Bitbake rev: d6a0ffdd583be3df734171d7e91d334f798a79ce)

Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/event.py

@@ -87,7 +87,7 @@ def fire_class_handlers(event, d):
     for name, handler in _handlers.iteritems():
         try:
             execute_handler(name, handler, event, d)
-        except BaseException:
+        except Exception:
             continue
 
 ui_queue = []