Address PR review: catch KeyError in response parsing

- Add KeyError to except clause when parsing JSON response to handle
  missing 'code' or 'message' keys
- Add explanatory comment on pre-existing except-pass pattern

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: MichaelGHSeg

segment/analytics/request.py

@@ -100,7 +100,7 @@ def post(write_key, host=None, gzip=False, timeout=15, proxies=None, oauth_manag
         payload = res.json()
         log.debug('received response: %s', payload)
         raise APIError(res.status_code, payload['code'], payload['message'], res)
-    except ValueError:
+    except (ValueError, KeyError):
         log.error('Unknown error: [%s] %s', res.status_code, res.reason)
         raise APIError(res.status_code, 'unknown', res.text, res)
 

segment/analytics/test/test_consumer.py

@@ -155,7 +155,7 @@ def test_request_retry(self):
         try:
             self._test_request_retry(consumer, api_error, 1)
         except APIError:
-            pass
+            pass  # Expected: 400 is non-retryable, so the error propagates here
         else:
             self.fail('request() should not retry on client errors')