bitbake: process: Allow BBUIEventQueue to exit cleanly

Currently the monitoring thread exits with some error code or runs indefinitely. Allow
closure of the pipe its monitoring to have the thread exit cleanly/silently.

(Bitbake rev: 930d077637928213e13a07c78fee3bf7a8c37ebf)

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

bitbake/lib/bb/server/process.py

@@ -499,9 +499,14 @@ class BBUIEventQueue:
     def startCallbackHandler(self):
         bb.utils.set_process_name("UIEventQueue")
         while True:
-            self.reader.wait()
-            event = self.reader.get()
-            self.queue_event(event)
+            try:
+                self.reader.wait()
+                event = self.reader.get()
+                self.queue_event(event)
+            except EOFError:
+                # Easiest way to exit is to close the file descriptor to cause an exit
+                break
+        self.reader.close()
 
 class ConnectionReader(object):