Test ab-err-xs0006-002

The pipeline

<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:ex="http://test" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result">
      <result/>
   </p:output>
   <p:for-each>
      <p:with-input>
         <source/>
      </p:with-input>
      <p:output port="result"/>
      <p:sink/>
   </p:for-each>
</p:declare-step>