fix: dev: [vps] insert line return in error message for clarity !minor

Signed-off-by: Valentin Lab <valentin.lab@kalysto.org>

bin/vps

@@ -436,8 +436,8 @@ cmdline.spec:backup:cmd:mailcow:run() {
 
     for f in  mysql-backup mirror-dir; do
         [ -e "/etc/cron.d/$f" ] || {
-            err "Can't find '/etc/cron.d/$f'." \
-                "Have you forgotten to run 'vps install backup BACKUP_HOST' ?"
+            err "Can't find '/etc/cron.d/$f'."
+            echo "  Have you forgotten to run 'vps install backup BACKUP_HOST' ?" >&2
             return 1
         }
 
@@ -492,8 +492,8 @@ cmdline.spec:backup:cmd:compose:run() {
 
     local cron_line args
     if ! cron_line=$(docker exec myc_cron_1 cat /etc/cron.d/rsync-backup | grep "\* \* \*"); then
-        err "Can't find cron_line in cron container." \
-            "Have you forgotten to run 'compose up' ?"
+        err "Can't find cron_line in cron container."
+        echo "  Have you forgotten to run 'compose up' ?" >&2
         exit 1
     fi