Catch serial.tools.list_ports import exception for unsupported platforms

[sqbi-q]

My fix for #969.

Summary by CodeRabbit

• Bug Fixes
  • Improved application startup when serial port discovery is unavailable.
  • Added clearer diagnostic messages for serial port detection errors and warnings.

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[coderabbitai]

📝 Walkthrough

Walkthrough

serial.tools.list_ports now loads conditionally. Import failures produce diagnostic messages instead of preventing meshtastic.util from loading.

Changes

Serial port import handling

Layer / File(s)	Summary
Guard serial port import meshtastic/util.py	The serial.tools.list_ports import now catches ImportError and prints error and platform-related warning messages.

Estimated code review effort: 2 (Simple) | ~5 minutes

Suggested reviewers: ianmcorvidae

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: handling the import exception for serial.tools.list_ports on unsupported platforms.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@meshtastic/util.py`:
- Around line 22-27: Initialize list_ports to None in the ImportError handler,
then update findPorts() to return an empty list before calling
list_ports.comports() when the fallback is unavailable. Preserve normal port
discovery when the import succeeds, and add a regression test covering the
failed-import path.

🪄 Autofix

Fix all unresolved CodeRabbit comments on this PR:

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

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 259d213f-e2ae-44d0-8fef-3c2de5187898

📥 Commits

Reviewing files that changed from the base of the PR and between ae71047 and e9ab622.

📒 Files selected for processing (1)

• meshtastic/util.py

[coderabbitai]

🩺 Stability & Availability | 🟠 Major | ⚡ Quick win

Define a fallback for failed imports.

When this import raises ImportError, the handler does not initialize a usable fallback. However, findPorts() still calls serial.tools.list_ports.comports() at Line 162. On an unsupported platform, findPorts() can raise NameError or AttributeError instead of returning no ports.

Store a sentinel such as list_ports = None, check it at the start of findPorts(), and return an empty list before accessing the unavailable module. Add a regression test for the failed-import path.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@meshtastic/util.py` around lines 22 - 27, Initialize list_ports to None in
the ImportError handler, then update findPorts() to return an empty list before
calling list_ports.comports() when the fallback is unavailable. Preserve normal
port discovery when the import succeeds, and add a regression test covering the
failed-import path.