github.com/davecgh/go-spew/spew is set to the newest version, a bit
newer than required by testify. Updated from version 6 Nov 2015 to
27 Jun 2017.

github.com/stretchr/objx is not updated - testify uses version
from 27 May 2014 which is older than 28 Sep 2015 used now (latest
actually). In practice there is only a tiny difference - one method was
removed in new version.