diff -r 9ac96b9fa76e -r 8f07f5a9c3de mercurial/error.py
--- a/mercurial/error.py	Tue Nov 03 09:56:02 2020 -0800
+++ b/mercurial/error.py	Sat Nov 07 21:50:28 2020 -0800
@@ -130,6 +130,13 @@
     __bytes__ = _tobytes
 
 
+class WorkerError(Exception):
+    """Exception raised when a worker process dies."""
+
+    def __init__(self, status_code):
+        self.status_code = status_code
+
+
 class InterventionRequired(Hint, Exception):
     """Exception raised when a command requires human intervention."""