Our script for building static media files could pull in the wrong

version of Django, based on the local environment and which versions

were installed. If the system had Django 1.6 installed, it would prefer

that over Django 1.11, even if running on Python 3. This happened

because we explicitly tell it which version to import, and that was 1.6.

It would still try to load in Django 1.11 media, just through the 1.6

process.
We also weren't using the right string types when manipulating the

environment. While not a huge problem in practice, in theory it could

cause issues.
And finally, we weren't initializing the Django setup procedures when on

Django 1.11.
This change fixes all that. We now set the desired Django version

depending on whether we're on Python 2.7 or 3.x. In time, this will be

the same version for both.
It's important to note that this will not fix building static media

files. There are some huge differences between the media shipped by

Django 1.6 and 1.11, and this impacts our own media building in

significant ways. The work required to fix that is very much

in-progress. This change just fixes the initial start of the static

media building process.

Tested starting off the media building process on Django 1.6 and 1.11,

on Python 2.7 and 3.5-3.7.