chg: [nextcloud] add a check for creation of ``occ`` command.

nextcloud/actions/occ

@@ -19,8 +19,12 @@ if ! [ -e "$SERVICE_DATASTORE/var/www/html/occ" ]; then
     ## Last, we do not want the relation web-proxy to run in this
     ## bare-minimum nextcloud run AND we will use occ to set some info
     ## in this very same relation.
-    compose --without-relation="$SERVICE_NAME":web-proxy run \
+    compose --debug --without-relation="$SERVICE_NAME":web-proxy run \
             --rm --entrypoint /entrypoint.sh "$SERVICE_NAME" apache >&2 || true
+    if ! [ -e "$SERVICE_DATASTORE/var/www/html/occ" ]; then
+        err "Expected last command to create /var/www/html/occ"
+        exit 1
+    fi
 fi