Replace assert statements with method calls

The unittest/testtools library defines assert methods which behave
similarly to using assert calls. However, they print more descriptive
error messages when they are triggered, helpfully printing both what
they received and what they expected.

Also, hurrah for emacs keyboard macros.

Change-Id: Ifbc54d3ead41eafed66be2a5b021fd4407a80a37
Reviewed-on: https://review.openstack.org/35967
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Approved: James E. Blair <corvus@inaugust.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Tested-by: Jenkins