[Pkg-mailman-hackers] Bug#962284: mailman: File "/usr/lib/mailman/cron/cull_bad_shunt", line 77 SyntaxError with Python 3

[Dominic Hargreaves]

On Sun, Jun 07, 2020 at 11:30:55AM -0600, Joe Pfeiffer wrote:
> Dominic Hargreaves writes:
> >
> >Mailman 2 will never support python 3 and it has been removed from
> >unstable and testing (see mailman3 for the future, but bear in mind it's
> >very much not a transparent upgrade).
> 
> Yeah, the amount of work I anticipate for the switch is why I've been
> procrastinating.  I wasn't aware it had been removed from unstable and
> testing; it sounds like I'm going to have to bite the bullet sooner
> rather than later....

Yep, I sympathise - I have the same issue (speaking as one of the
maintainers of alioth-lists.debian.net as well as some other installs.
(For the avoidance of doubt, I'm not the maintainer of the mailman
package.)

I believe it's already been determined that python 2 will not be shipped
with bullseye.

> >That said, as far as I can tell even
> >in unstable, /usr/bin/python is still pointing to /usr/bin/python2.7,
> >so you must have manually changed the link in /usr/bin/python behind
> >the packaging system's back?
> 
> At this point, update-alternatives lists python3 as the "auto"
> alternative, so that appears to be the default (I'm nothing resembling
> an expert on Debian policies or packaging, so it's entirely possible
> I'm reading more into that than I should).

This confused me, since Python in Debian doesn't have alternatives set
up - but a quick web search reveals various people suggesting receipes
for setting this up by hand, so at a guess you must have done this,
aybe following something like this?

https://stackoverflow.com/questions/43062608/how-to-update-alternatives-to-python-3-without-breaking-apt

The default you're seeing is not a part of the Debian system.

I mention this merely as a clarification for future readers of the
bug report. Glad to see that you've managed to get things working
for yourself :)

Cheers
Dominic