[release-3.8] Raise exception when CreateFleet doesn't return any instance #578

[lukeseawalker]

Description of changes

• Raise an exception when CreateFleet doesn't return any instance and the error list in the CreateFleet contains only one error entry. The exception raised is built with the same error code coming from the CreateFleet response, so that this error code can be set into the reason when putting the Slurm nodes into DOWN. This is useful to avoid to trigger the fast capacity failover (error code InsufficientInstanceCapacity) when the CreateFleet call doesn't return any instance because of throttling (error code RequestLimitExceeded).

Tests

• unit tests added
• manual tested on running cluster

References

n/a

Checklist

• Make sure you are pointing to the right branch.
• If you're creating a patch for a branch other than develop add the branch name as prefix in the PR title (e.g. [release-3.6]).
• Check all commits' messages are clear, describing what and why vs how.
• Make sure to have added unit tests or integration tests to cover the new/modified code.
• Check if documentation is impacted by this change.

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[codecov]

Codecov Report

All modified lines are covered by tests ✅

Comparison is base (659d56d) 89.93% compared to head (c80a925) 90.03%.

Additional details and impacted files

@@               Coverage Diff               @@
##           release-3.8     #579      +/-   ##
===============================================
+ Coverage        89.93%   90.03%   +0.10%     
===============================================
  Files               16       16              
  Lines             2692     2699       +7     
===============================================
+ Hits              2421     2430       +9     
+ Misses             271      269       -2     

Flag	Coverage Δ
unittests	90.03% <100.00%> (+0.10%)	⬆️

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Files	Coverage Δ
src/slurm_plugin/fleet_manager.py	93.51% <100.00%> (+1.10%)	⬆️
src/slurm_plugin/instance_manager.py	100.00% <100.00%> (ø)

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