bitbake: server/process: Improve idle loop exit code

When idle handlers want to exit, returning "False" isn't very clear
and also causes challenges with the ordering of the removing the idle
handler and marking that no async command is running.

Use a specific class to signal the exit condition allowing clearer code
and allowing the async command to be cleared after the handler has been
removed, reducing any opportunity for races.

(Bitbake rev: 102e8d0d4c5c0dd8c7ba09ad26589deec77e4308)

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

bitbake/lib/bb/command.py

@@ -128,22 +128,19 @@ class Command:
             else:
                 return False
         except KeyboardInterrupt as exc:
-            self.finishAsyncCommand("Interrupted")
-            return False
+            return bb.server.process.idleFinish("Interrupted")
         except SystemExit as exc:
             arg = exc.args[0]
             if isinstance(arg, str):
-                self.finishAsyncCommand(arg)
+                return bb.server.process.idleFinish(arg)
             else:
-                self.finishAsyncCommand("Exited with %s" % arg)
-            return False
+                return bb.server.process.idleFinish("Exited with %s" % arg)
         except Exception as exc:
             import traceback
             if isinstance(exc, bb.BBHandledException):
-                self.finishAsyncCommand("")
+                return bb.server.process.idleFinish("")
             else:
-                self.finishAsyncCommand(traceback.format_exc())
-            return False
+                return bb.server.process.idleFinish(traceback.format_exc())
 
     def finishAsyncCommand(self, msg=None, code=None):
         if msg or msg == "":