[SOLVED] While using your page (mostly copying) from bash at ~:
mysqldump u segmarian -h segmarian.mysql.pythonanywhere-services.com --set-gtid-purged=OFF --no-tablespaces 'segmarian$XXXXXX' > db-backup.sql
returns
mysqldump: [ERROR] unknown variable 'database=segmarian$XXXXXX'