docs: def packet_xml(url_encoded_ivorn=None):
      """
      Returns the XML packet contents stored for a given IVORN.
  
      The required IVORN should be appended to the URL after ``/xml/``
      in :ref:`URL-encoded <url-encoding>` form.
      """
      # Handle Apache / Debug server difference...
      # Apache conf must include the setting::
      #   AllowEncodedSlashes NoDecode
      # otherwise urlencoded paths have
      # double-slashes ('//') replaced with single-slashes ('/').
      # However, the werkzeug simple-server decodes these by default,
      # resulting in differing dev / production behaviour, which we handle here.
  
      ivorn = validate_ivorn(url_encoded_ivorn)
      xml = db_session.query(Voevent.xml).filter(
          Voevent.ivorn == ivorn
      ).scalar()
      r = make_response(xml)
      r.mimetype = 'text/xml'
      return r