Comment 4 for bug 1605948

Setting up mysql-server-5.7 (5.7.13-0ubuntu0.16.04.2) ...
Renaming removed key_buffer and myisam-recover options (if present)
Job for mysql.service failed because the control process exited with error code. See "systemctl status mysql.service" and "journalctl -xe" for " for details.
invoke-rc.d: initscript mysql, action "start" failed.
dpkg: error processing package mysql-server-5.7 (--configure):
 subprocess installed post-installation script returned error exit status 1
Errors were encountered while processing:
 mysql-server-5.7
E: Sub-process /usr/bin/dpkg returned an error code (1)

‚óŹ mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: inactive (dead) (Result: exit-code) since Mon 2016-07-25 15:03:20 BST; 9min ago
 Main PID: 29823 (code=exited, status=0/SUCCESS)

Jul 25 15:03:19 XXXX systemd[1]: mysql.service: Unit entered failed state.
Jul 25 15:03:19 XXXX systemd[1]: mysql.service: Failed with result 'exit-code'.
Jul 25 15:03:20 XXXX systemd[1]: mysql.service: Service hold-off time over, scheduling restar
Jul 25 15:03:20 XXXX systemd[1]: Stopped MySQL Community Server.
Jul 25 15:03:20 XXXX systemd[1]: mysql.service: Start request repeated too quickly.
Jul 25 15:03:20 XXXX systemd[1]: Failed to start MySQL Community Server.

My mySQL was working perfectly well until today's upgrade.