There were a handful of issues affecting CentOS 8 and stream-8, both in

the actual installer as well as our test harness:

The crb repo used by newer centos releases is called powertools in

  8 and stream-8.
There's no epel-next-release repo.
For the install tests, we need to update yum to point at

  vault.centos.org because they've removed these from the primary

  mirror.

Ran unit tests.
Ran install tests for centos8/stream-8.