Issue #16491: IDLE now prints chained exception tracebacks.

diff --cc Lib/idlelib/run.py
Simple merge

diff --cc Misc/NEWS
index cbf5cb6d02a32a26a289eb15d198c57da6e52f7a,e3fd61c8911bfa143affcb17d5f52963e96e105e..73809ec6adc1e5df5054a4213eac50e249cbeaf1
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -209,8 -139,8 +209,10 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #16491: IDLE now prints chained exception tracebacks.
+ 
 +- fcntl: add F_DUPFD_CLOEXEC constant, available on Linux 2.6.24+.
 +
  - Issue #15972: Fix error messages when os functions expecting a file name or
    file descriptor receive the incorrect type.