why is bytearray treated so inefficiently by pickle?

[Terry Reedy]

On Nov 30, Irmen de Jong opened a tracker issue with a patch improve 
bytearray pickling.
http://bugs.python.org/issue13503

Yesterday, Dec 5, Antoine Pitrou applied a revised fix.
http://hg.python.org/cpython/rev/e2959a6a1440/
The commit message:
"Issue #13503: Use a more efficient reduction format for bytearrays with 
pickle protocol >= 3. The old reduction format is kept with older 
protocols in order to allow unpickling under Python 2."

-- 
Terry Jan Reedy