add. exception type UMQueryCallError to flag exceptional cases
add. exception type UMQueryCallError to flag exceptional cases

wikimedia/analytics-user-metrics,rfaulkner/wikipedia_user_metrics,wikimedia/analytics-user-metrics,wikimedia/user_metrics,wikimedia/user_metrics,wikimedia/user_metrics,wikimedia/analytics-user-metrics,rfaulkner/wikipedia_user_metrics,rfaulkner/wikipedia_user_metrics