Kallithea on Python 3 has landed

[Mads Kiilerich]

After a lot of refactoring, reviews and testing, Python 3 migration has 
landed on the default development branch on 
https://kallithea-scm.org/repos/kallithea/ . The migration happens in 
aa6f17a53b49 to 01aca0a4f876, in a series of minimal and 
as-reviewable-as-possible steps (temporarily leaving things broken until 
everything is done).

It is a big change: a lot of code changed, and all the code that didn't 
change is also potentially influenced by the changes between Python 2 
and 3. Please help test it. Go as far as you dare with a test upgrade, 
and report any problems you see. That is the only way you can make sure 
it will work relatively smoothly for you when it finally gets released.

Upgrading should be trivial if you use the same virtualenv location as 
before. The only manual step is to change the .ini git_hook_interpreter 
to python3, and run /_admin/settings/mapping "Install Git hooks".

The documentation on https://kallithea.readthedocs.io/en/default/ has 
been updated. The three special Windows sections are however in a bad 
state. They need someone to validate and copy edit everything. If not, 
it seems like it would be better to delete these sections - rather leave 
it to people to figure it out instead of giving false information.

We plan to release Python 3 support soon, as Kallithea 0.6 .

Kallithea 0.5.x will be the last versions to support Python 2.

Thanks to Thomas for a lot of helping, reviewing and testing.

/Mads