Better error message when blocking query

[dveeden]

https://dev.mysql.com/doc/refman/5.7/en/writing-audit-plugins.html
This can be done by using my_message()

[sjmudd]

It may be convenient to provide a custom message maybe configurable via a global variable (default use what you have.)

This would be used to lead developers/administrators to the right "place" when they see this "unexpected message".

Perhaps implemented as:

mysql> SET GLOBAL maxdiskusage_message='Running out of free disk space. Contact <some_person_or_email_address> for more details.';