[RHELC-1269] Add diagnosis for failures in validating yum transaction

[pr-watson]

This PR adds a diagnosis field for when there is a failure during the validation of a yum transaction. The error raised is added to the diagnosis field which can sometimes come out as a list which is why we have a .join added.

Jira Issues: RHELC-1269

Checklist

• PR has been tested manually in a VM (either author or reviewer)
• Jira issue has been made public if possible
• [RHELC-] is part of the PR title
• GitHub label has been added to help with Release notes
• PR title explains the change from the user's point of view
• Code and tests are documented properly
• The commits are squashed to as few commits as possible (without losing data)
• When merged: Jira issue has been updated to Release Pending if relevant

[has-bot]

/packit test --labels sanity

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (dd31177) 94.46% compared to head (8dd569d) 94.46%.
Report is 13 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1081   +/-   ##
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  Coverage   94.46%   94.46%           
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  Files          48       48           
  Lines        4568     4568           
  Branches      815      815           
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  Hits         4315     4315           
  Misses        178      178           
  Partials       75       75           

Flag	Coverage Δ
centos-linux-7	89.66% <ø> (ø)
centos-linux-8	90.65% <ø> (ø)
centos-linux-9	90.71% <ø> (ø)

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[Venefilyn]

Unit tests failing