Dropping Python2 (except buildtime)

[Andrew Bartlett]

G'Day,

Just a quick note to say that I have a merge request in to finally drop
our python2 support, beyond the build process.  (We already stopped
testing it a month or so ago). 

This also removes --extra-python and will make it easier for whatever
changes need to be made for our python helper library names etc to be
made, as we will then always be in py3 mode. 

If there is any reason this shouldn't go in please let me know soon, as
I would like to push it soon after 4.10.0 is released as the tests.py
changes keep needing rebase work.

This will also allow much of our custom py2/py3 compatibility work to
be undone (in future patches) and so move our code back to a more
idiomatic python, which will help with long-term maintenance. 

Metze,

This extends https://gitlab.com/samba-team/samba/merge_requests/262
which you asked to be delayed until 4.10.0.  Do you have any more
concerns after 4.10.0 is out?

Thanks!

Andrew Bartlett
-- 
Andrew Bartlett
https://samba.org/~abartlet/
Authentication Developer, Samba Team         https://samba.org
Samba Development and Support, Catalyst IT   
https://catalyst.net.nz/services/samba