bitbake: server/process: Fix waitEvent() calls with 0 timeout

You might think Queue.Queue.get(True, 0) would return an event immediately
if present and otherwise return. It doesn't, it immediately "times out"
and returns with nothing from the queue.

The behaviour we want is not to wait but return anything present which is
what .get(False) does so map to this.

This fixes some odd behaviour observed in some of the tinfoil selftests.

(Bitbake rev: 412bfab8721ea317898a1974f6a7a0d0bea763df)

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

bitbake/lib/bb/server/process.py

@@ -253,6 +253,8 @@ class ProcessEventQueue(multiprocessing.queues.Queue):
         try:
             if not self.server.is_alive():
                 return self.getEvent()
+            if timeout == 0:
+                return self.get(False)
             return self.get(True, timeout)
         except Empty:
             return None