package:mysql-server-5.7:5.7.21-0ubuntu0.16.04.1
Setting up mysql-server-5.7 (5.7.21-0ubuntu0.16.04.1) ...
update-alternatives: using /etc/mysql/mysql.cnf to provide /etc/mysql/my.cnf (my.cnf) in auto mode
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 details.
invoke-rc.d: initscript mysql, action "start" failed.
● mysql.service - MySQL Community Server
   Loaded: loaded (/lib/systemd/system/mysql.service; enabled; vendor preset: enabled)
   Active: activating (auto-restart) (Result: exit-code) since Sun 2018-03-11 21:24:32 IST; 9ms ago
  Process: 6963 ExecStartPre=/usr/share/mysql/mysql-systemd-start pre (code=exited, status=1/FAILURE)

Mar 11 21:24:32 akshay-VirtualBox systemd[1]: mysql.service: Control process...1
Mar 11 21:24:32 akshay-VirtualBox systemd[1]: Failed to start MySQL Communit....
Mar 11 21:24:32 akshay-VirtualBox systemd[1]: mysql.service: Unit entered fa....
Mar 11 21:24:32 akshay-VirtualBox systemd[1]: mysql.service: Failed with res....
Hint: Some lines were ellipsized, use -l to show in full.
dpkg: error processing package mysql-server-5.7 (--configure):
 subprocess installed post-installation script returned error exit status 1