[PATCH] Switch to python 3

[Alen Siljak]

Thanks for the consideration, John. I'm happy to push for adoption of Python 3 and use that exclusively (as I'm fresh in the Python world). 
Sebastien might still be supporting v2 in some projects so let's see what he has to add.

> Sent: Friday, March 16, 2018 at 3:26 PM
> From: "John Ralls" <jralls at ceridwen.us>
> To: "Julian Wollrath" <jwollrath at web.de>
> Cc: gnucash-devel at gnucash.org
> Subject: Re: [PATCH] Switch to python 3
>
> For further discussion here, though, particularly for Sébastien de Menten and Alen Siljak: Is it OK to convert to Python-3 only or should the bindings support both Python-2.7 and Python-3