New python3-defaults uploaded making Python 3.13 default

[Julian Gilbey <julian@d-and-j.net>]

Hi all,

Just to let you know that Matthias and Stefano upload python3-defaults
3.13.1 to unstable earlier this week, making Python 3.13 the default.
I just got a FTBFS bug report which turned out to be because the build
used python3 to perform an action, and python3.12 succeeds on this but
python3.13 fails.  It took me a while to discover the cause, so just
wanted to share this information to save other people time if they
receive similar FTBFS reports.

Best wishes,

   Julian