NC15 & Preview Generator 2.1.0 on Ubuntu 18.04
https://help.nextcloud.com/t/dconf-error-root-cache-dconf-permission-denied/49245/2
https://help.nextcloud.com/t/error-imagickexception-not-authorized/49258
https://github.com/rullzer/previewgenerator/issues/154
@rullzer please