take return of mkdir into account, throw exception on failure
take return of mkdir into account, throw exception on failure

Signed-off-by: Arthur Schiwon <9ae9918f3cbf5a90ebc25affe594cc53853aee42@arthur-schiwon.de>

andreas-p/nextcloud-server,andreas-p/nextcloud-server,nextcloud/server,nextcloud/server,andreas-p/nextcloud-server,nextcloud/server,andreas-p/nextcloud-server,nextcloud/server,andreas-p/nextcloud-server