According to the Python	Policy
(/usr/share/doc/python3/python-policy.txt.gz with quote marks
introduced for clarity):

  The keyword "all" is no longer to be used since using version numbers
  is clearer than all and encodes more information. The keyword "all"
  must be ignored for Python 3 versions.

This can be resolved by simply removing the X-Python3-Version: all
field from debian/control.

Best wishes,

   Julian

We believe that the bug you reported is fixed in the latest version of
python-outcome, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1003822@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Robie Basak <robie@justgohome.co.uk> (supplier of updated python-outcome package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Sun, 03 Jul 2022 13:53:52 +0100
Source: python-outcome
Binary: python3-outcome
Architecture: source
Version: 1.2.0-1
Distribution: unstable
Urgency: medium
Maintainer: Robie Basak <robie@justgohome.co.uk>
Changed-By: Robie Basak <robie@justgohome.co.uk>
Description:
 python3-outcome - capture the outcome of Python function calls
Closes: 1003822
Changes:
 python-outcome (1.2.0-1) unstable; urgency=medium
 .
   * New upstream release.
   * Drop "X-Python3-Version: all" since it is deprecated. Closes: #1003822.
     Thanks to Julian Gilbey.
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