Revert "concurrent.futures.process: avoid ref cycle in _sendback_result"

This reverts commit ef30122.

Author: ebonnal

Lib/concurrent/futures/process.py

@@ -210,13 +210,9 @@ def _sendback_result(result_queue, work_id, result=None, exception=None,
         result_queue.put(_ResultItem(work_id, result=result,
                                      exception=exception, exit_pid=exit_pid))
     except BaseException as e:
-        result_queue.put(
-            _ResultItem(
-                work_id,
-                exception=_ExceptionWithTraceback(e, e.__traceback__),
-                exit_pid=exit_pid
-            )
-        )
+        exc = _ExceptionWithTraceback(e, e.__traceback__)
+        result_queue.put(_ResultItem(work_id, exception=exc,
+                                     exit_pid=exit_pid))
 
 
 def _process_worker(call_queue, result_queue, initializer, initargs, max_tasks=None):