fix(python/flask): catch AIGuardAbortError explicitly (BaseException-safe)

[avara1986]

Motivation

Companion to DataDog/dd-trace-py#17941 (chore(core): deprecate raising_dispatch).

That PR introduces a new `DDBlockException(BaseException)` hierarchy and re-parents `AIGuardAbortError` under it:

```
BaseException
├── Exception ← what `except Exception:` matches
└── DDBlockException ← NEW, BaseException-derived
├── BlockingException
└── AIGuardAbortError ← was Exception-derived, now BaseException-derived
```

The motivation in dd-trace-py is to prevent generic `except Exception:` handlers in user code from accidentally swallowing AI Guard block decisions. As a side effect, the existing pattern in this weblog stops working:

```python
except Exception as e:
if isinstance(e, AIGuardAbortError):
return ..., 403
else:
return ..., 500
```

Because `AIGuardAbortError` is no longer an `Exception` subclass, `except Exception:` does not match it (same way it doesn't match `KeyboardInterrupt`). The block is never entered, the `isinstance` check never runs, the response is never returned, and the request reaches the test as no-status — which is exactly what is breaking `tests/ai_guard/test_ai_guard_sdk.py::Test_Evaluation::test_deny` and `::test_abort` against `python@4.9.0-rc1`.

Changes

`utils/build/docker/python/flask/app.py` — restructure the AI Guard evaluate endpoint:

• Catch `AIGuardAbortError` explicitly (by class identity, so it works regardless of base class).
• Keep the broad `except Exception:` for the 500 fallback.

This is more idiomatic Python and forward-compatible with the dd-trace-py exception hierarchy change.

Workflow

1. ⚠️ Create your PR as draft ⚠️
2. Work on you PR until the CI passes
3. Mark it as ready for review
   • Test logic is modified? -> Get a review from RFC owner.
   • Framework is modified, or non obvious usage of it -> get a review from R&P team

🚀 Once your PR is reviewed and the CI green, you can merge it!

🛟 #apm-shared-testing 🛟

Reviewer checklist

• Anything but `tests/` or `manifests/` is modified ? I have the approval from R&P team
• A docker base image is modified?
  • the relevant `build-XXX-image` label is present
• A scenario is added, removed or renamed?
  • Get a review from R&P team

[github-actions]

CODEOWNERS have been resolved as:

utils/build/docker/python/flask/app.py                                  @DataDog/apm-python @DataDog/asm-python @DataDog/system-tests-core

[datadog-datadog-prod-us1]

🎉 All green!

❄️ No new flaky tests detected
🧪 All tests passed

_{This comment will be updated automatically if new data arrives.
🔗 Commit SHA: b99be7e | Docs | Datadog PR Page | Give us feedback!}

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 2ddd4d6573

ℹ️ About Codex in GitHub

Codex has been enabled to automatically review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

When you sign up for Codex through ChatGPT, Codex can also answer questions or update the PR, like "@codex address that feedback".