Eliminate use of nose

[mcepl]

I am a maintainer of Python packages in openSUSE, and I am on my crusade of eliminating nose1 from our distribution. When I look at its repository on https://github.com/nose-devs/nose, the last release 1.3.7 was on 2 Jun 2015, and even the last commit on the master branch was on 4 Mar 2016.

This patch eliminates dependency on nose, which has been unnecessary for a long time. Resulting tests are pure unittest-based ones requiring nothing than the standard library.