Bug#1000200: reportbug-gtk: cannot close reportbug (on fluxbox)

CC'ing the python3.9 maintainer.

On 22.12.2021 00.39, Nis Martensen wrote:
> Hello GTK/Gnome experts,
> 
> Would you be able to help with #1000200? Reportbug's GTK UI does not
> close properly any more. It works fine in bullseye, and there was no
> change in reportbug that could have caused this change in behaviour.
> 
>> Michael Hatzold hat am 19.11.2021 geschrieben:
>>> When using reportbug-gtk I now cannot close it (the window) anymore, not even
>>> after sending the email.  I can minimize it, but not close. I have to open a VT
>>> and pkill or ctrl-C it (when opened in a VT)
>>>
>>> It used to work, and klicking the "x" in the title bar should close it.

Update: The bug was introduced with the upload of python3.9 3.9.8-1 to
unstable on 7 November. Downgrading python3.9 to version 3.9.7-4 fixes
the problem.

Next tasks: Identify which change between python 3.9.7 and 3.9.8 is
responsible, and find out which package needs to change to fix the problem.