[debian-mysql] Bug#843959: tell user how to workaround in warning message

[積丹尼 Dan Jacobson]

severity 843959 important
found 843959 5.7.20-1
thanks

This is so frustrating each time.

The user has to check the bugtracker each time to know what to do.

Please upon failure, print out the message

'Try "systemctl enable mysql && aptitude safe-upgrade && systemctl disable mysql"'

Or say apt-get instead of aptitude, etc.