Direct STDERR output when listing crontab to /dev/null

When installing crontab on systems using fcron the output from STDERR is captured and inserted into the updated crontab. An example from a fresh install follows. While fcron does not outright complain about this when saving the file, it is messy and quite avoidable.

2019-02-03 13:18:18  INFO listing magento's fcrontab
#~ MAGENTO START 7cd0a74c421051ec6cce8936eb9edd02
* * * * * /usr/lib64/php7.2/bin/php /var/www/magento/bin/magento cron:run 2>&1 | grep -v "Ran jobs by schedule" >> /var/www/magento/var/log/magento.cron.log
* * * * * /usr/lib64/php7.2/bin/php /var/www/magento/update/cron.php >> /var/www/magento/var/log/update.cron.log
* * * * * /usr/lib64/php7.2/bin/php /var/www/magento/bin/magento setup:cron:run >> /var/www/magento/var/log/setup.cron.log
#~ MAGENTO END 7cd0a74c421051ec6cce8936eb9edd02

Author: danielatdattrixdotcom

lib/internal/Magento/Framework/Crontab/CrontabManager.php

@@ -182,7 +182,7 @@ private function cleanMagentoSection($content)
     private function getCrontabContent()
     {
         try {
-            $content = (string)$this->shell->execute('crontab -l');
+            $content = (string)$this->shell->execute('crontab -l 2>/dev/null');
         } catch (LocalizedException $e) {
             return '';
         }