import oneflow in custom_exit (#4736)

Co-authored-by: oneflow-ci-bot <69100618+oneflow-ci-bot@users.noreply.github.com>

oneflow/init.py

@@ -80,6 +80,8 @@ __original_exit__ = sys.exit
 
 def custom_exit(returncode):
     if returncode != 0:
+        import oneflow
+
         oneflow._oneflow_internal.MasterSendAbort()
     __original_exit__(returncode)