mapnik/tests/data/broken_maps/db_host_broken.xml

<!DOCTYPE Map [
<!ENTITY db_name "gis">
<!ENTITY db_host "/no/socket/here">
]>
<Map background-color="red" minimum-version="0.7.2">
  <Layer name="some_layer" status="on" srs="+proj=merc +datum=WGS84  +k=1.0 +units=m +over +no_defs">
    <Datasource>
      <Parameter name="type">postgis</Parameter>
      <Parameter name="host">/no/socket/here</Parameter>
      <Parameter name="password">SECRET</Parameter>
      <Parameter name="dbname">gis</Parameter>
    </Datasource>
  </Layer>

</Map>