function _getUpdateIssueRequestData(fieldName, fieldValue, evt){
            var requestData = {"issues[0].id": vars.issueId};

            if(fieldName === "labelIds"){
                requestData["attachingLabelIds"] = _getIdProps(evt.added);
                requestData["detachingLabelIds"] = _getIdProps(evt.removed);
            } else {
                requestData[fieldName] = fieldValue;
            }

            if(fieldName === "dueDate"){
                requestData["isDueDateChanged"] = true;
            }

            return requestData;
        }
Returns request data to update issue info.

@param fieldName
@param fieldValue
@param evt
@returns {Hash Table}
@private