python-backrefs fails to build with Python 3.14.0a1.

Problem:
It's trying to download unicode data not present in the sdist, and as the build environment is offline, fails:

  Downloading: ftp://ftp.unicode.org/Public/16.0.0/ucd/UnicodeData.txt --> /builddir/build/BUILD/python-backrefs-5.7.post1-build/backrefs-5.7.post1/tools/unicodedata/16.0.0/UnicodeData.txt
  Failed: ftp://ftp.unicode.org/Public/16.0.0/ucd/
  Downloading: http://www.unicode.org/Public/16.0.0/ucd/UnicodeData.txt --> /builddir/build/BUILD/python-backrefs-5.7.post1-build/backrefs-5.7.post1/tools/unicodedata/16.0.0/UnicodeData.txt
  Failed: http://www.unicode.org/Public/16.0.0/ucd/
  Failed to acquire all needed Unicode files!

Solution:
Unicode 16.0.0 should be added to the tarball by upstream.

https://docs.python.org/3.14/whatsnew/3.14.html

For the build logs, see:
https://copr-be.cloud.fedoraproject.org/results/@python/python3.14/fedora-rawhide-x86_64/08189179-python-backrefs/

For all our attempts to build python-backrefs with Python 3.14, see:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/package/python-backrefs/

Testing and mass rebuild of packages is happening in copr.
You can follow these instructions to test locally in mock if your package builds with Python 3.14:
https://copr.fedorainfracloud.org/coprs/g/python/python3.14/

Let us know here if you have any questions.

Python 3.14 is planned to be included in Fedora 43.
To make that update smoother, we're building Fedora packages with all pre-releases of Python 3.14.
A build failure prevents us from testing all dependent packages (transitive [Build]Requires),
so if this package is required a lot, it's important for us to get it fixed soon.

We'd appreciate help from the people who know this package best,
but if you don't want to work on this now, let us know so we can try to work around it on our side.