[IMPROV] Use 'assertEqual' and 'assertRaisesRegex'

In Python 3 'assertEquals' and 'assertRaisesRegexp' have been
deprecated. The new 'assertEqual' already exists in Python 2 but for
'assertRaisesRegex' a alias method was added (but not used everywhere).

Change-Id: Icfd0a61a48cc25886701ffa8b91f54881af553f0