fix(bootstrapper): log specific error types in wheel cache lookup

[LalatenduMohanty]

Replace bare except Exception in _download_wheel_from_cache() with three handlers so logs distinguish why a cache lookup failed:

• ResolverException → INFO (wheel not found)
• RequestException → WARNING (network error)
• Exception → WARNING (unexpected error, e.g. bad wheel file, I/O)

All three still return (None, None) to preserve existing behavior.

Closes: #1025

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: 667d1a17-cf10-4b5d-a7fa-d6eba93d3815

📥 Commits

Reviewing files that changed from the base of the PR and between e6784f8 and 7568402.

📒 Files selected for processing (2)

• src/fromager/bootstrapper.py
• tests/test_bootstrapper.py

📝 Walkthrough

Walkthrough

The PR replaces a broad except Exception in Bootstrapper._download_wheel_from_cache() with three specific handlers: ResolverException (logs INFO and returns (None, None)), requests.exceptions.RequestException (logs WARNING about network errors and returns (None, None)), and a final except Exception for unexpected errors (logs WARNING and returns (None, None)). It adds pytest coverage in tests/test_bootstrapper.py for resolver-not-found, various requests errors, unexpected exceptions, download-time errors, and an early-return when cache_wheel_server_url is empty.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the main change: replacing a bare exception handler with specific error type logging in the wheel cache lookup function.
Description check	✅ Passed	The description clearly explains the three exception handlers and their log levels, directly addressing the issue of distinguishing network errors from genuine cache misses.
Linked Issues check	✅ Passed	The code changes fully address issue #1025: ResolverException returns INFO, RequestException and other exceptions return WARNING, and all branches preserve the (None, None) return behavior.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to differentiating error handling in _download_wheel_from_cache() and adding corresponding test coverage; no unrelated modifications detected.

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Inline comments:
In `@tests/test_bootstrapper.py`:
- Around line 304-318: The test test_resolver_exception_returns_none should also
assert that ResolverException triggers the "did not find wheel" INFO log path:
when calling Bootstrapper._download_wheel_from_cache with
fromager.resolver.resolve patched to raise ResolverException, capture logs
(e.g., using caplog) and assert an INFO-level record contains the phrase "did
not find wheel" (or the exact message emitted by _download_wheel_from_cache) in
addition to asserting the return value is (None, None); update the test to
reference ResolverException and bt._download_wheel_from_cache so the log
assertion focuses on that code path.
- Around line 396-406: The test test_no_cache_url_returns_none does not assert
that the resolver is not invoked; update it to mock or spy on
fromager.resolver.resolve and assert it was not called when
Bootstrapper.cache_wheel_server_url is empty; specifically instantiate
bootstrapper.Bootstrapper, set cache_wheel_server_url = "", call
_download_wheel_from_cache with the Requirement/Version, and then assert
fromager.resolver.resolve (or the injected resolver used by Bootstrapper) had
zero invocations to validate the early-return guard.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: c95b0344-a5aa-404c-ab53-0466adcc8d05

📥 Commits

Reviewing files that changed from the base of the PR and between 9a24ab8 and 2199620.

📒 Files selected for processing (2)

• src/fromager/bootstrapper.py
• tests/test_bootstrapper.py

[jlarkin09]

LGTM

[rd4398]

This looks good to me!

[mergify]

This pull request has merge conflicts that must be resolved before it can be merged.
@LalatenduMohanty please rebase your branch.

[rd4398]

This looks good!