Use logging in the knotty ui, and pass the log record across directly

This kills firing of Msg* events in favor of just passing along LogRecord
objects.  These objects hold more than just level and message, but can also
have exception information, so the UI can decide what to do with that.

As an aside, when using the 'none' server, this results in the log messages in
the server being displayed directly via the logging module and the UI's
handler, rather than going through the server's event queue.  As a result of
doing it this way, we have to override the event handlers of the base logger
when spawning a worker process, to ensure they log via events rather than
directly.

(Bitbake rev: c23c015cf8af1868faf293b19b80a5faf7e736a5)

Signed-off-by: Chris Larson <chris_larson@mentor.com>
Signed-off-by: Richard Purdie <rpurdie@linux.intel.com>

bitbake/bin/bitbake

@@ -164,7 +164,8 @@ Default BBFILES are the .bb files in the current directory.""")
     configuration.pkgs_to_build.extend(args[1:])
     configuration.initial_path = os.environ['PATH']
 
-    logger.addHandler(event.LogHandler())
+    loghandler = event.LogHandler()
+    logger.addHandler(loghandler)
 
     #server = bb.server.xmlrpc
     server = bb.server.none
@@ -190,6 +191,8 @@ Default BBFILES are the .bb files in the current directory.""")
     server.BitBakeServerFork(cooker, cooker.server, serverinfo, cooker_logfile)
     del cooker
 
+    logger.removeHandler(loghandler)
+
     # Setup a connection to the server (cooker)
     serverConnection = server.BitBakeServerConnection(serverinfo)