Merge: #23745: handle duplicate MIME parameter names in new parser.

diff --cc Misc/NEWS
index 2b9ce2e7443e11a7847095acdba9d84373fc4c42,ebac8d52f65380e62accbace5bbe47fd777096fe..ff81056a1c20d971cec639a2d113246d5089987d
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -56,12 -21,9 +56,15 @@@ Core and Builtin
  Library
  -------
  
+ - Issue #23745: The new email header parser now handles duplicate MIME
+   parameter names without error, similar to how get_param behaves.
+ 
 +- Issue #22117: Fix os.utime(), it now rounds the timestamp towards minus
 +  infinity (-inf) instead of rounding towards zero.
 +
 +- Issue #14260: The groupindex attribute of regular expression pattern object
 +  now is non-modifiable mapping.
 +
  - Issue #23792: Ignore KeyboardInterrupt when the pydoc pager is active.
    This mimics the behavior of the standard unix pagers, and prevents
    pipepager from shutting down while the pager itself is still running.