#7963: fix error message when 'object' called with arguments.

Patch by Alexander Belopolsky.
#7963: fix error message when 'object' called with arguments.
Fix error messages.
#13700: Make imap.authenticate with authobject work.

This fixes a bytes/string confusion in the API which prevented
custom authobjects from working at all.

Original patch by Erno Tukia.
Merge: #13700: Make imap.authenticate with authobject work.

This fixes a bytes/string confusion in the API which prevented
custom authobjects from working at all.

Original patch by Erno Tukia.