Python 2 is no longer supported, thus usage of six can be removed.
Also, This removes B314 test from documentation because its actual
implementation was already removed[1].
[1] 9dbeefb55eb55a9baa481ec6d6293527d46e04a5
Change-Id: Ib01714e6462470dd5c3f6f06b52a3afeff573696