Handle command responses without "ok" field. PYTHON-574

Author: ajdavis

pymongo/helpers.py

@@ -116,6 +116,10 @@ def _unpack_response(response, cursor_id=None, as_class=dict,
 def _check_command_response(response, reset, msg="%s", allowable_errors=[]):
  """Check the response to a command for errors.
  """
+ if "ok" not in response:
+ # Server didn't recognize our message as a command.
+ raise OperationFailure(response.get("$err"))
+
  if not response["ok"]:
  if "wtimeout" in response and response["wtimeout"]:
  raise TimeoutError(msg % response["errmsg"])