worker: raise exception instead of calling sys.exit() with child's code When a worker process returns an error code, we would call `sys.exit()` with that exit code on the main process. The `SystemExit` exception would then get caught in `scmutil.callcatch()`, which would return that error code. The comment there says "Commands shouldn't sys.exit directly", which I agree with. This patch changes it so we raise a specific exception when a worker fails so we can catch instead. I think that means that `SystemExit` is now always an internal error. (I had earlier thought that this call to `sys.exit()` was from within the child process until Matt Harbison made me look again, so thanks for that!) Differential Revision: https://phab.mercurial-scm.org/D9287

--- a/mercurial/worker.py	Tue Nov 03 09:56:02 2020 -0800
+++ b/mercurial/worker.py	Sat Nov 07 21:50:28 2020 -0800
@@ -300,7 +300,7 @@
     if status:
         if status < 0:
             os.kill(os.getpid(), -status)
-        sys.exit(status)
+        raise error.WorkerError(status)
     if hasretval:
         yield True, retval