fix: source TemplateRenderError from canonical exceptions module (CodeQL #783)

[ramseymcgrath]

Summary

Fixes the one real correctness bug surfaced during a triage of the GitHub code scanning (CodeQL) findings.

pcileech_generator.py imported TemplateRenderError from the pcileechfwgenerator.templating package, whose __init__ sets TemplateRenderError = None in its ImportError fallback (src/templating/__init__.py:19-22). If that fallback ever triggers, the handler at pcileech_generator.py:698 becomes except None, which raises TypeError at exception-match time and masks the real SystemVerilog-generation error (CodeQL alert #783, py/useless-except).

The fix imports TemplateRenderError from pcileechfwgenerator.exceptions, where it is defined unconditionally. It is the same class object that template_renderer actually raises (template_renderer.py:16 imports it from exceptions), so exception matching is unchanged — the name simply can never be None again.

Changes

• src/device_clone/pcileech_generator.py — move TemplateRenderError from the templating import to the exceptions import.
• tests/test_pcileech_generator_template_error_import.py — regression test that reproduces the templating ImportError fallback (templating.TemplateRenderError = None) and asserts the handler name stays a valid exception class.

Verification

• Regression test fails before the fix (TemplateRenderError became None) and passes after — TDD-confirmed.
• All 61 related pcileech_generator / template_renderer tests pass; no regressions.

Triage notes (not in this PR)

The remaining critical-level CodeQL alerts were reviewed and determined to be false positives, to be dismissed on GitHub rather than code-changed:

• #1098 base.py:129 (wrong-arguments) — call arity is satisfied; only a redundant double-format.
• fix validation #252 attribute_access.py:198 (hash-unhashable) — dominated by an explicit isinstance(..., Hashable) guard.
• #702-705, #1059-1060 string_utils.py (shell-command-constructed-from-input) — pure logging/formatting helpers; no output reaches a shell (safe_format returns text; no shell=True/os.system/os.popen anywhere).

Separately, two create_subprocess_shell sites (system_status.py, build_orchestrator.py) are a defense-in-depth hardening opportunity to restore the documented argv-only invariant — out of scope here.

[Copilot]

Pull request overview

This PR fixes a real correctness issue in the PCIe firmware generation orchestrator (pcileech_generator) where an except TemplateRenderError handler could become except None if pcileechfwgenerator.templating fell back on its ImportError path, masking the underlying SystemVerilog generation error (CodeQL #783).

Changes:

• Import TemplateRenderError from pcileechfwgenerator.exceptions (where it is always defined) instead of from pcileechfwgenerator.templating (where it can be set to None under fallback).
• Add a regression test that simulates templating.TemplateRenderError = None and asserts pcileech_generator.TemplateRenderError remains a valid exception class and matches the canonical exception type.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/device_clone/pcileech_generator.py	Sources TemplateRenderError from the canonical exceptions module to prevent except None failures under templating fallback.
tests/test_pcileech_generator_template_error_import.py	Adds a regression test covering the degraded templating-package state and ensuring exception matching remains correct.

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[codecov]

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