Proper regular expression for server error message
===

I am making a ajax call and I am getting error from the server.

Now the problem is I am getting the below message


    HTTP Status 756 - Error while processing the request.
    
    --------------------------------------------------------------------------------
    
    type Status report
    
    message Error while processing the request.
    
    description Cannot find message associated with key http.756



And I want to get only error message from the complete error report not all the text above. How can I do that ?