From now on, the line
from __future__ import unicode_literals
should be contained in every single Python file lest we run into any more 2.x/3.x issues.
Going forward, we're likely to develop on 3.x only and would likely miss subtle bugs otherwise.
From now on, test_download will run these tests. That means we benefit not only from the networking setup in there, but also from the other tests (for example test_all_urls to find problems with _VALID_URLs).
