grc/misc_utils/gsm_message_printer.xml

<?xml version="1.0"?>
<block>
  <name>Message printer</name>
  <key>gsm_message_printer</key>
  <import>import gsm</import>
  <make>gsm.message_printer()</make>

  <sink>
    <name>msgs</name>
    <type>message</type>
  </sink>
</block>