chore: optimize something

[starnop]

Describe what this PR does / why we need it

1. optimize the error log with the reason for failing to pull the Seaelr Image
2. we should expose any interface definitions including the constants we use

Does this pull request fix one issue?

Describe how you did it

Describe how to verify it

Special notes for reviews

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (2b4c47a) 19.31% compared to head (2f8af03) 19.31%.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2079   +/-   ##
=======================================
  Coverage   19.31%   19.31%           
=======================================
  Files          96       96           
  Lines        8978     8978           
=======================================
  Hits         1734     1734           
  Misses       7019     7019           
  Partials      225      225           

Impacted Files	Coverage Δ
pkg/clusterfile/clusterfile.go	25.34% <0.00%> (ø)

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[kakaZhou719]

LGTM