Fix: Handle Empty Response Body in HTTP Error Cases

[zxzinn]

Problem

When the Cohere API returns an HTTP error (e.g., 500 Internal Server Error) with an empty response body, the SDK crashes with a JSONDecodeError instead of properly handling the error. This occurs because the error handling code attempts to parse the empty response body as JSON without checking if it's parseable first.

Error Flow

# Current problematic code structure in raw_client.py
try:
    if _response.status_code == 500:
        raise InternalServerError(
            body=construct_type(
                object_=_response.json(),  # ⚠️ Throws JSONDecodeError if body is empty
            )
        )
    ...
    _response_json = _response.json()
except JSONDecodeError:
    # This catch block is too late - it can't catch the error from line above
    raise ApiError(...)

Production Error Example

From Sentry issue:

ApiError: status_code: 500, body:
  at cohere/v2/client.py:971

During handling of the above exception, another exception occurred:
JSONDecodeError: Expecting value: line 1 column 1 (char 0)
  at cohere/v2/client.py:935 in _response.json()

Solution

Introduced a _safe_json_parse() helper function that gracefully handles JSON parsing failures:

def _safe_json_parse(response: typing.Any) -> typing.Any:
    """
    Safely parse JSON from HTTP response.
    Returns parsed JSON or response text if parsing fails.
    """
    try:
        return response.json()
    except JSONDecodeError:
        return response.text