Since there is no demo or us site anymore we can simplify the structure
somewhat by moving the sandbox one directory up

c06e1df wrongly changed the imports to relative imports, as settings
isn't a module (but probably should be). Reverting those changes for
now.

python-modernize (https://github.com/mitsuhiko/python-modernize) is a
useful wrapper around 2to3 which comes with sane defaults.

The fixes below were generated by running

    python-modernize --compat-unicode -w .

and then fixing all lint errors.

This reverts ac7e8ee