Finding it very difficult to move pyexiv2 code from Python 2 to Python 3

[Chris Angelico]

On Fri, Aug 21, 2020 at 3:21 AM Chris Green <cl at isbd.net> wrote:
> It's actually more subtle and complicated than the OS changing or not
> changing the default Python version.  There are quite a lot of
> questions about exactly this on the Ubuntu lists.  All the OS python
> code in Ubuntu 20.04 is now Python 3 but there are some other things
> which I have installed (such as Mercurial) which still depend on
> Python 2.  One can see what is affected by doing:-
>
>     $ sudo apt remove python2 --simulate
>
> This shows a mixture of old (and no longer needed) libraries that
> would go with Python 2 but it also shows some things like Mercurial
> that I need.

That seems odd. According to packages.ubuntu.com, Focal (20.04) is
shipping Mercurial 5.3.1, and since version 5.2, Mercurial has
supported Python 2.7 or 3.5+. However, it seems that the dependencies
for the mercurial package specify python2 and no reference to python3.

https://packages.ubuntu.com/focal/mercurial

Fortunately, the *next* release of Ubuntu fixes this:

https://packages.ubuntu.com/groovy/mercurial

It depends on Python 3.8 instead. No idea why the 20.04 release insists on 2.7.

ChrisA