title: Groovy XmlSlurper: Find attribute name by attribute value in XML
body: <p>How can I find an attribute name in XML structure by attribute value using Groovy <strong>XmlSlurper/XmlParser</strong>.
  Let's say we have XML:</p>
  
  <pre><code>&lt;root&gt;
      &lt;item id="Correction"&gt;
          &lt;desc value_err="Error_3"&gt;&lt;/desc&gt;
      &lt;/item&gt;
      &lt;item id_err="Error_2"&gt;
          &lt;desc /&gt;
      &lt;/item&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p>I need to find attribute name by value (Initial task: find list of nodes where attribute value like 'Error_').
  e.g "Error_2" -> <strong>id_err</strong> and "Error_3" -> <strong>value_err</strong></p>
  
  <p>The only solution I found iteration through all Node attributes map. 
  Is there any GPath for it?</p>
  
  <p>Small remark: we're not able to change structure of XML. This is external exception API.</p>