Break up RemoteRunner.call_process and repair its error messages

[appleweiping]

Fixes #399.

RemoteRunner.call_process reports C901 ... is too complex (14) against the --max-complexity=10 the lint job uses. Most of that came from two error-translation blocks nested inside the happy path.

This extracts _rpc_error_message, _handle_rpc_error and _process_remotely as methods, plus _group_created_indices as a module-level function, leaving call_process as the request/response flow. The grouping loop becomes a setdefault instead of a try/except KeyError.

The restructuring itself changes no behaviour: pytest python/tests reports the same 242 passed, 10 skipped before and after.

Two error paths that never worked

Pulling the block apart made both visible.

The UNAVAILABLE advice was being discarded. It was written as:

msg = f'Failed to connect to "{self.processor_name}", check '
"that the service is running and the address is "
"correctly configured."

The second and third lines are expression statements, not continuations of the assignment, so they evaluate and are thrown away. Operators saw a message that stopped mid-sentence at check . They are now part of the string.

The closed-channel message could never be produced. The check was e == ValueError('Cannot invoke RPC on closed channel!'). ValueError defines no __eq__, so this is always False:

>>> ValueError('x') == ValueError('x')
False

It now compares the type and str(e).

Testing

Adds python/tests/processing/test_runners.py covering both messages, the absence of a specific message for other status codes, and the index grouping — 5 tests, suite goes to 247 passed / 10 skipped.

These pin the corrected behaviour rather than reproducing the old one: the message construction was inline inside call_process, so there was nothing to assert against before the extraction. The evidence that the old paths were dead is the language behaviour shown above.

Running the lint job's flags over python goes from 4 findings to 3. The two that remain are pre-existing E501/E303 in deployment.py, untouched here.

🤖 Generated with Claude Code

[appleweiping]

Validated the latest head aa12cc5 locally.

• The focused runner test file passed all 5 tests.
• Python compilation passed for the updated runner module.
• The diff check passed.

This covers the refactored RemoteRunner call, the repaired error messages, and the grouping helper. Please review the updated branch.