Silence mrtg weathermap warning

mrtg/tasks/weathermap.yml

@@ -87,7 +87,7 @@
     name: "create weathermap"
     minute: "*/5"
     # yamllint disable-line rule:line-length
-    job: "cd /opt/weathermap && /opt/weathermap/weathermap --config /etc/weathermap.conf --output /var/www/mrtg/weathermap.png"
+    job: "cd /opt/weathermap && /opt/weathermap/weathermap --config /etc/weathermap.conf --output /var/www/mrtg/weathermap.png &>/dev/null"
     state: present
     user: mrtg
     cron_file: weathermap