bitbake: event: prevent unclosed file warning in print_ui_queue

Use logger.addHandler(), rather than assigning an array of Handlers
to the loggers handlers property directly, to avoid a warning from
Python 3 about unclosed files:

$ bitbake
Nothing to do.  Use 'bitbake world' to build everything, or run 'bitbake --help' for usage information.
WARNING: /home/joshuagl/Projects/poky/bitbake/lib/bb/event.py:143: ResourceWarning: unclosed file <_io.TextIOWrapper name='/home/joshuagl/Projects/poky/build/tmp/log/cooker/qemux86/20161004094928.log' mode='a' encoding='UTF-8'>
  logger.handlers = [stdout]

(Bitbake rev: 1e23b1f1a80066223b98e18b163840051ac74944)

Signed-off-by: Joshua Lock <joshua.g.lock@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/event.py

@@ -143,16 +143,16 @@ def print_ui_queue():
             if isinstance(event, logging.LogRecord):
                 if event.levelno > logging.DEBUG:
                     if event.levelno >= logging.WARNING:
-                        logger.handlers = [stderr]
+                        logger.addHandler(stderr)
                     else:
-                        logger.handlers = [stdout]
+                        logger.addHandler(stdout)
                     logger.handle(event)
                     msgprint = True
         if msgprint:
             return
 
         # Nope, so just print all of the messages we have (including debug messages)
-        logger.handlers = [stdout]
+        logger.addHandler(stdout)
         for event in ui_queue:
             if isinstance(event, logging.LogRecord):
                 logger.handle(event)