bitbake: event/server: Add _uiready flag to handle missing error messages

If you start and suspend a bitbake execution so the bitbake lock is held,
then try and run "bitbake -w '' X", you will see bitbake return an error exit
code but print no message about what happened at all.

The reason is that the -w option creates a "UI" which swallows the messages. The
code which handles this exit failure mode thinks a UI has printed the messages
and therefore doesn't do so.

This adds in an extra parameter to the UI registration code so that we
can figure out whether its a primary UI or not and base decisions on whether
to display information on that instead. This fixes the error shown above and
some bizarre failures on the Yocto Project Autobuilder.

[YOCTO #8239]

(Bitbake rev: d1d60a68c2de40c2984d5040d14251c1be121b0b)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/server/process.py

@@ -97,7 +97,7 @@ class ProcessServer(Process, BaseImplServer):
     def run(self):
         for event in bb.event.ui_queue:
             self.event_queue.put(event)
-        self.event_handle.value = bb.event.register_UIHhandler(self)
+        self.event_handle.value = bb.event.register_UIHhandler(self, True)
 
         bb.cooker.server_main(self.cooker, self.main)