BLACKHOLE is no longer active in 10.1 by default, mysql_upgrade not handling the situation

MariaDB 10.1 binary packages no longer come with BLACKHOLE storage engine compiled in, it comes as a loadable plugin now instead, which is not loaded by default.

When upgrading a 10.0 instance with a BLACKHOLE table in it mysql_upgrade detects the problem, but doesn't fix it.

[...]

Phase 5/6: Checking and upgrading tables

Processing databases

information_schema

performance_schema

test

test.t1

Error    : Unknown storage engine 'BLACKHOLE'

error    : Corrupt

Repairing tables

test.t1

Error    : Unknown storage engine 'BLACKHOLE'

error    : Corrupt

[...]

Suggested fix: make mysql_upgrade check I_S.TABLES for unknown storage engine messages in TABLE_COMMENTS, and issue appropriate INSTALL [PLUGIN|SONAME] statements for the bundled engine plugins before actually trying to check and repair tables.