Dropping python 2.7 support in gtk-doc (requiring python 3.X)

[Stefan Sauer <ensonic hora-obscura de>]

Hi,

Having support for both python 2.7 and python 3.X in gtk-doc makes the
code ugly and is beyond what I can test. I am considering to require
python >=3.4 für the next gtk-doc release. Would that be a problem for
anyone?

To also give some extra motivation - Since a few month I am working on
gtkdoc-mkhtml which is a pure python drop-in replacement for
gtkdoc-mkhtml+gtkdoc-fixxref. This is not using docbook xslt anymore and
it won't shell out to tools to do syntax highlighting. This new tool
would need some changes to work with python 2.7 too.

I'll write more about gtkdoc-mkhtml2 soon, especially how you can test
this with your modules, but if you have questions please ask (on
gtk-doc-list@ or in #gtkdoc in irc).

Stefan