Sometimes your Laravel setup misses migration tabes for additional databases and this causes issues running php artisan migrate and this also causes issues running php artisan schema:dump for that database. You will get errors like

Error Output:
================
mysqldump: Couldn't find table: "migrations"
at vendor/symfony/process/Process.php:267

So there are a few things to do or you can do. You can install a migrations table first. Then you can run the dump

php artisan migrate:install --database=mysql_publish_testing

INFO  Migration table created successfully.
php artisan schema:dump --database=mysql_publish_testing    
mysqldump: unknown variable 'column-statistics=0'

INFO  Database schema dumped successfully.