htmlreport: Add new command that creates HTML reports of SIG test case failures

[brianmcarey]

What this PR does / why we need it:

This new command will primarily used by periodic prow jobs to generate daily reports on each specific SIG's tescase failures. These reports will help SIG members to identify and tackle the faiures.

The reports will be stored on the kubevirt GCS bucket and can be linked to from the ci-health README where we track the number of SIG e2e failures

Here is an example report for SIG Network:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

/cc @dhiller @xpivarc

Checklist

This checklist is not enforcing, but it's a reminder of items that could be relevant to every PR.
Approvers are expected to review this list.

• Design: A design document was considered and is present (link) or not required
• PR: The PR description is expressive enough and will help future contributors
• Code: Write code that humans can understand and Keep it simple
• Refactor: You have left the code cleaner than you found it (Boy Scout Rule)
• Upgrade: Impact of this change on upgrade flows was considered and addressed if required
• Testing: New code requires new unit tests. New features and bug fixes require at least on e2e test
• Documentation: A user-guide update was considered and is present (link) or not required. You want a user-guide update if it's a user facing feature / API change.
• Community: Announcement to kubevirt-dev was considered

Release note:

[sourcery-ai]

Hey there - I've reviewed your changes - here's some feedback:

• Avoid using global variables (SigFailures and jobRegex); instead declare them inside Generate so the function is reentrant and testable.
• On critical failures (e.g. reading results.json or creating the output file), return an error or exit rather than just logging, and defer closing any opened files to prevent resource leaks.
• When printing the CLI success message, include the full path to the generated report file (including its filename) instead of just the directory for clearer feedback.

Prompt for AI Agents

Please address the comments from this code review:
## Overall Comments
- Avoid using global variables (SigFailures and jobRegex); instead declare them inside Generate so the function is reentrant and testable.
- On critical failures (e.g. reading results.json or creating the output file), return an error or exit rather than just logging, and defer closing any opened files to prevent resource leaks.
- When printing the CLI success message, include the full path to the generated report file (including its filename) instead of just the directory for clearer feedback.

## Individual Comments

### Comment 1
<location> `README.md:171` </location>
<code_context>
+
+### html-report command
+
+A command that generates html reports of test case failures per SIG. To create a report for SIG Compute failures:
+```
+go run ./cmd/html-report --sig compute --results-path ./output/kubevirt/kubevirt/results.json --path /tmp/
</code_context>

<issue_to_address>
Capitalize 'html' to 'HTML' for correctness.

Use 'HTML' instead of 'html' to align with standard terminology.
</issue_to_address>

### Comment 2
<location> `README.md:176` </location>
<code_context>
+go run ./cmd/html-report --sig compute --results-path ./output/kubevirt/kubevirt/results.json --path /tmp/
+```
+
+This should create a html report called sig-compute-failure-report.html under /tmp/.
</code_context>

<issue_to_address>
Use 'an HTML report' instead of 'a html report'.

Use 'an' before 'HTML' because it starts with a vowel sound, and ensure 'HTML' is capitalized.
</issue_to_address>

---

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[sourcery-ai]

suggestion (typo): Capitalize 'html' to 'HTML' for correctness.

Use 'HTML' instead of 'html' to align with standard terminology.

[sourcery-ai]

suggestion (typo): Use 'an HTML report' instead of 'a html report'.

Use 'an' before 'HTML' because it starts with a vowel sound, and ensure 'HTML' is capitalized.

[dhiller]

@brianmcarey great idea, and a very useful report. Some questions inline.

[dhiller]

Why is this comment necessary?

[brianmcarey]

@dhiller I've cleaned up the duplication - can you please take a look?

[dhiller]

Looks much better, thanks!

One last comment though - I believe it would be beneficial to use the junit library as mentioned here: #92 (comment)

[brianmcarey]

Looks much better, thanks!

One last comment though - I believe it would be beneficial to use the junit library as mentioned here: #92 (comment)

thanks for the great suggestion @dhiller - applied the changes and it helped to simplify things.

[dhiller]

Thanks @brianmcarey! 🎉