#20135: FAQ entry for list mutation.

This is a perennial question and something someone opens a ticket for probably
every other month or so, so I'm surprised we didn't already have a FAQ entry
for it.

The original patch was written by M. Votz, refined first by Ezio Melotti and
further refined by me.

--HG--
branch : 2.7
cleanup overflowing handling in unicode_decode_call_errorhandler and unicode_encode_ucs1 (closes #22518)

--HG--
branch : 2.7
add NEWS note for #22518

--HG--
branch : 2.7
merge heads

--HG--
branch : 2.7
fix overflow checking in PyString_Repr (closes #22519)

--HG--
branch : 2.7