Travis CI failing consistently in functional app-tests

[conorsch]

Bug

Description

The Travis CI tests have recently started failing consistently, related to the setUp def in the functional tests suite. Here's an example of a failing run. Notably, Travis just updated their Ubuntu Trusty base images two days ago, so it's quite possible that's related to the sudden and consistent failures.

Steps to Reproduce

1. Push changes to a feature branch.
2. Watch Travis run for that branch (https://travis-ci.org/freedomofpress/securedrop/branches, or swap out freedomofpress with your username if testing on a fork).
3. See Travis run bomb out on the functional_test.FunctionalTest.setUp(self) call.

Expected Behavior

Travis CI run passes.

Actual Behavior

Travis CI run fails.

Comments

There's a temporary workaround listed in the Travis announcement blog post that indicates we can fall back to the old Trusty image if we encounter problems. As a short-term solution, that sounds great, but the old image will be removed on 2017-09-01, so we'll need to solve the problem for real soon. #1655 may help with long-term solutions.