The mock third party library was needed for mock support in py2
runtimes. Since we now only support py36 and later, we can use the
standard lib unittest.mock module instead.
The method is known to be problematic, and it is going to be
Moreover, its usage in Sahara produces some nasty side-effects
when Python 3.x is used. The provisioning of the clusters ends
abruptly when sahara-engine tries to update the status in the
database, with a failure inside oslo_i18n.