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

[Mayank Modi]

I cant install or purge mysql5.7.
Gives me the error "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"

Always an error during update as well

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: mysql-server-5.7 5.7.21-0ubuntu0.16.04.1
ProcVersionSignature: Ubuntu 4.4.0-117.141-generic 4.4.114
Uname: Linux 4.4.0-117-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
AptOrdering:
 mysql-server-5.7: Configure
 mysql-server: Configure
 NULL: ConfigurePending
Architecture: amd64
Date: Mon May 7 13:24:48 2018
DpkgHistoryLog:
 Start-Date: 2018-05-07 13:24:37
 Commandline: apt-get install libgmp-dev
 Requested-By: mayankmodi (1000)
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2016-10-10 (573 days ago)
InstallationMedia: Ubuntu 15.10 "Wily Werewolf" - Release amd64 (20151021)
Logs.var.log.daemon.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: ['ib_buffer_pool', 'ib_logfile0', 'ts1', 'ca-key.pem', 'auto.cnf', 'ibdata1', 'mysql', 'Movies', 'ib_logfile1', 'sys', 'server-cert.pem', 'client-key.pem', 'performance_schema', 'public_key.pem', 'ca.pem', 'private_key.pem', 'ibtmp1', 'client-cert.pem', 'server-key.pem', 'debian-5.7.flag', 'ts', 'firstproject']
ProcCmdline: BOOT_IMAGE=/boot/vmlinuz-4.4.0-117-generic root=UUID=3ff5a174-9b25-41f5-b9a1-d00a79f2f9da ro quiet splash vt.handoff=7
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.4
 apt 1.2.26
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)

[Apport retracing service (apport)]

Thank you for taking the time to report this crash and helping to make this software better. This particular crash has already been reported and is a duplicate of bug #1769584, so is being marked as such. Please look at the other bug report to see if there is any missing information that you can provide, or to see if there is a workaround for the bug. Additionally, any further discussion regarding the bug should occur in the other report. Please continue to report any other bugs you may find.