I'm getting constant errors as the below message but I'm not sure where to start by fixing this issue:
[2016-12-15 02:35:01] setup-cron.ERROR: Could not locate magento/magento2-base/composer.json file.
It happened the same for me when Magento 2 was cloned from the git repository. As the documentation mentions, in such case you should run only one cron job, the
* * * * * /usr/bin/php /var/www/magento2/bin/magento cron:run | grep -v "Ran jobs by schedule" >> /var/www/magento2/var/log/magento.cron.log
because the other two are for those who installed Magento from the downloadable package.
Known issue, it has been discussed on github.
Check here: https://github.com/magento/devdocs/issues/778