Unicode problem with export of literal contents

[Jens Lechtenboerger]

Hi there,

consider this piece code, where unicode-file.org contains umlauts
(say, just the word “Lechtenbörger”):

(org-export-string-as
 (with-temp-buffer
   (insert-file-contents-literally "unicode-file.org")
   (buffer-string))
 'html t)

With Org 9.6.1 from Emacs master, I get the following warning, and I
am asked to select a coding system:

> These default coding systems were tried to encode the following
> problematic characters in the buffer ‘ *temp*’:
> ...

With previous Org versions, this did not happen, export would just
work.  Note that I insert contents literally because I do not want
‘find-file-hook’, automatic uncompression, etc. (which are avoided
according to the doc string of insert-file-contents-literally).

Could the old behavior be restored?

Best wishes
Jens