package mysql-server-5.7 5.7.21-0ubuntu0.16.04.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Vivek Soni]

This crashes my software update every time I do update via software update.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: mysql-server-5.7 5.7.21-0ubuntu0.16.04.1
ProcVersionSignature: Ubuntu 4.4.0-116.140-generic 4.4.98
Uname: Linux 4.4.0-116-generic i686
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: i386
Date: Sun Mar 18 18:48:42 2018
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2016-05-08 (681 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release i386 (20151021)
Logs.var.log.daemon.log:

Logs.var.log.mysql.error.log:
MySQLConf.etc.mysql.conf.d.mysql.cnf: [mysql]
MySQLConf.etc.mysql.conf.d.mysqldump.cnf:
 [mysqldump]
 quick
 quote-names
 max_allowed_packet = 16M
MySQLConf.etc.mysql.mysql.conf.d.mysqld_safe_syslog.cnf:
 [mysqld_safe]
 syslog
MySQLVarLibDirListing: ['DATABASE', 'ib_logfile1', 'debian-5.7.flag', 'DBMSFinal', 'mysql_upgrade_info', 'ib_buffer_pool', 'auto.cnf', 'ib_logfile0', 'ibdata1']
ProcCmdline: BOOT_IMAGE=/boot/vmlinuz-4.4.0-116-generic root=UUID=3dace278-b1db-4184-b03a-5b955a8b2a86 ro quiet splash vt.handoff=7
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.4
 apt 1.2.25
SourcePackage: mysql-5.7
Title: package mysql-server-5.7 5.7.21-0ubuntu0.16.04.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)