mysqlhotcopy fails when "databases = all" (deprecate method?)

The failure is caused by mysqlhotcopy trying and failing to hot-copy the performance_schema table:

Debug: su root -c "/usr/bin/mysqlhotcopy --quiet --allowold --regexp /.*/./.*/ /var/backups/mysql/hotcopy"
Warning: DBD::mysql::db do failed:  command denied to user 'root'@'localhost' for table 'accounts' at /usr/bin/mysqlhotcopy line 523.
Warning: Failed to hotcopy all mysql databases

This has been reported in DEBBUG-735014 as well as upstream (six years ago). Upstream eventually responded that mysqlhotcopy is deprecated and not distributed anymore with MySQL 5.7.

I think with regards to this, the fact that mysqlhotcopy only supports then MyISAM or ARCHIVE engines, and the InnoDB engine being the default nowadays, I suggest we remove support for mysqlhotcopy from the handler and replace it with support for XtraBackup or MariaDB Backup (the latter being a more featureful fork of the former). Both are packaged in Debian.

Edited by Jérôme Charaoui
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