[CentOS] Updating microcode_ctl froze Centos7

Mon Jun 15 20:25:33 UTC 2020
Robin Lee <robinlee at mailbox.org>

On Fri, 2020-06-12 at 09:20 +0200, Robin Lee wrote:
> Today when I ran yum update two packages came up microcode_ctl
> and unbound-libs. The updating process went fine until it outputted 
> 
> Running transaction
>   Updating   : 2:microcode_ctl-2.1-61.6.el7_8.x86_64
> 
> then it just froze. I could no longer ssh to the machine and the
> console was just blank. I had to shut down it hard. It came back up
> seemingly fine. But yum update doesn't work anymore. It says "Error
> importing repomd.xml from base/7/x86_64: Damaged repomd.xml file"
> I looked at the logs, but journalctl only shows the latest boot on
> this
> machine. 
> 
> So I guess I have three questions
> - Any idea what happened with the update process?
> - How can I repair repomd.xml?

Now that yum is up and running again it tells me the following 

"There are unfinished transactions remaining. You might consider
running yum-complete-transaction, or "yum-complete-transaction --
cleanup-only" and "yum history redo last", first to finish them. If
those don't work you'll have to try removing/installing packages by
hand (maybe package-cleanup can help)."

Doing "yum-complete-transaction --cleanup-only" should be safe, right?
To clean up the botched microcode_ctl update and after that set it
among excluded packages.

/Robin