Why not consider Warns as errors? Here is an example of a Warn that can be returned for a malformed CustomerQueryRq which prevents the query from executing. 
```
<?xml version=\"1.0\" ?><QBXML><QBXMLMsgsRs><CustomerQueryRs statusCode=\"500\" statusSeverity=\"Warn\" statusMessage=\"The query request has not been fully completed. There was a required element (&quot;bleech&quot;) that could not be found in QuickBooks.\" /></QBXMLMsgsRs></QBXML>
```