This helper method doesn't exist, so just looks like a method call
rather than checking an expectation.  The tests started failing when
python-mock introduced code to check for this particular mistake, likely
in response to this blog post:

http://engineeringblog.yelp.com/2015/02/assert_called_once-threat-or-menace.html

setting up a trusty chroot.

configuration files (it seems some have been edited for Travis's trusty
image).

specific links right.

for style checks.