worker: properly report errors from worker processes (issue3982)

mercurial/worker.py

@@ -89,11 +89,8 b' def _posixworker(ui, func, staticargs, a'
                 os._exit(0)
             except KeyboardInterrupt:
                 os._exit(255)
-            except: # re-raises (close enough for debugging anyway)
-                try:
-                    ui.traceback()
-                finally:
-                    os._exit(255)
+                # other exceptions are allowed to propagate, we rely
+                # on lock.py's pid checks to avoid release callbacks
         pids.append(pid)
     pids.reverse()
     os.close(wfd)