fix(models/gemini): handle non-JSON error messages from Gemini API

[Ratish1]

Description

Avoid a raw JSONDecodeError when the Gemini API returns an empty or non-JSON error message (for example on an invalid API key).

This PR:

• Catches json.JSONDecodeError when parsing error.message, logs a warning with context (error_message=<...> | Gemini API returned non-JSON error), and re-raises the original genai.errors.ClientError with the JSON error as the explicit cause.

• Adds a unit test (test_stream_handles_non_json_error) to verify a non-JSON error is logged and the original ClientError is propagated

Related Issues

#1024

Documentation PR

N/A

Type of Change

Bug fix

Testing

How have you tested the change? Verify that the changes do not break functionality or introduce warnings in consuming repositories: agents-docs, agents-tools, agents-cli

• I ran hatch run prepare
• I ran hatch fmt --formatter and hatch fmt --linter
• I ran the unit test: pytest -q tests/strands/models/test_gemini.py::test_stream_handles_non_json_error -> passed

Checklist

• I have read the CONTRIBUTING document
• I have added any necessary tests that prove my fix is effective or my feature works
• I have updated the documentation accordingly
• I have added an appropriate example to the documentation to outline the feature, or no new docs are needed
• My changes generate no new warnings
• Any dependent changes have been merged and published

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[Ratish1]

Hello @dbschmigelski , can the github actions be run with your approval, so the workflow passes. Thanks.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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