Travis are deprecating their Precise build stack and we need to look at migrating to Trusty.

See this blog post for info: https://blog.travis-ci.com/2017-07-11-trusty-as-default-linux-is-coming

We currently use Precise (previous default) in the Container environment for 31; and Precise in the GCE environment for stables, and master.

As of this morning (18th July 2017), Travis switched from Precise to Trusty as their default environment. This means that some tests are broken.

From August they'll be deprecating the Precise Container builds entirely from August.

As a interim, we can hard-code the distribution to precise. I'm doing that in MDL-59570.

In this issue we should:

• ensure that we can migrate to Trusty; and
• consider backporting MDL-58844 to 31.