Improve the setup of test runs.

Review Request #10537 — Created April 17, 2019 and submitted — Latest diff uploaded

Review Board

This makes a few key changes to test runs in an effort to avoid a few
types of warnings and failures on newer versions of Python and Django,
and when the network is down.

We now disable the smart mail spoofing on test runs, avoiding DNS
lookups any time fake e-mail is being sent. We also now avoid loading
extensions unnecessarily on each test run.

Django 2.0 deprecation warnings are now filtered out on test runs,
avoiding a lot of unwanted noise.

We also now override the nose options to avoid doing doctests, which
triggered an error inspecting some non-UTF-8 data files during test

Unit tests pass on Python 2.7/Django 1.6 and Python 3.7/Django 1.11.

Tested Review Board and extension tests.