fix(iris): handle testcase exec errors

[jspark2000]

Description

Close #1939

Additional context

sandbox testcase 실행 결과가 success가 아닐 경우 발생한 오류 코드와 내용을 포함하도록 수정합니다

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• [x] Read the Contributing Guidelines
• [x] Read the Contributing Guidelines and follow the Commit Convention
• [x] Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• [x] Ideally, include relevant tests that fail without this PR but pass with it.