We used Drush on our server without any problems up until now. Actually we didn't do / change anything relating to Drush.
But now, on every Drush command we issue, we only get an error like so:
Drush command terminated abnormally due to an unrecoverable error.
Same error also occurs for
Drush status. Only
drush --version shows "Drush version: 6.6.0".
We installed drush via Composer. And the server is already restarted.
What can we do about this problem, which is a huge problem for us?