email/charset.py has convert() function to incorporate
using different charset for input and output for a
language like Japanese.  Because the email user agent
in Japan frequently use characters outside the range of
legitimate JIS charset, these messages are shunted in
mailman delivery.  Here is a patch to handle this case
by replacing the characters by '?' using the 'errors'
parameter in unicode/encode functions.

This patch includes the unicode string conversion patch
in #1368247.