on Windows instead of silently truncate them.

Removed no longer used _PyUnicode_HasNULChars().

on Windows instead of silently truncate them.

0-0xffff for empty data.

0-0xffff for empty data.

Patch by Andy Holst.

Patch by Andy Holst.

There are doubtless other debug messages in smtplib that would trigger an
error if they were tested, but this fixes the things we do now test,
which is good enough for now.

Patch by Gavin Chappell and Maciej Szulik.

This fix is a superset of the functionality introduced by the issue #19494
enhancement, and supersedes that fix.  Instead of a new handler, we have a new
password manager that tracks whether we should send the auth for a given uri.
This allows us to say "always send", satisfying #19494, or track that we've
succeeded in auth and send the creds right away on every *subsequent* request.
The support for using the password manager is added to AbstractBasicAuth,
which means the proxy handler also now can handle prior auth if passed
the new password manager.

Patch by Akshit Khurana, docs mostly by me.