package mysql-server-5.7 5.7.16-0ubuntu0.16.04.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Pawel Orzechowski]

Mysql upgrade from 14.04 to 16.04 fails with mysql-server not being installed.
Error that comes is unknown variable 'thread_concurrency=8'.
One needs to comment thread_concurrency=8 parameter in /etc/my/my.cnf

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: mysql-server-5.7 5.7.16-0ubuntu0.16.04.1
ProcVersionSignature: Ubuntu 3.13.0-96.143-generic 3.13.11-ckt39
Uname: Linux 3.13.0-96-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
Date: Wed Nov 2 09:39:57 2016
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2014-06-27 (859 days ago)
InstallationMedia: Ubuntu-Server 12.04.4 LTS "Precise Pangolin" - Release amd64 (20140204)
Logs.var.log.daemon.log:

MySQLConf.etc.mysql.conf.d.mysql.cnf: [mysql]
MySQLConf.etc.mysql.conf.d.mysqld_safe_syslog.cnf:
 [mysqld_safe]
 syslog
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: ['poczta', 'ib_logfile1', 'mysql_upgrade_info', 'chmurka', 'ibdata1', 'hasla', 'mysql', 'performance_schema', 'wiicp', 'projekty', 'ib_logfile0', 'debian-5.5.flag']
ProcCmdline: BOOT_IMAGE=/vmlinuz-3.13.0-96-generic root=/dev/mapper/vg01-root ro ipv6.disable=1
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.1
 apt 1.2.12~ubuntu16.04.1
SourcePackage: mysql-5.7
Title: package mysql-server-5.7 5.7.16-0ubuntu0.16.04.1 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: Upgraded to xenial on 2016-11-02 (0 days ago)

[Nish Aravamudan (nacc)]

Hello and thank you for filing this report!

So I believe you upgraded from MySQL 5.5/5.6 to 5.7 but indicated you wanted to keep your configuration files. However, this one stanza (thread_concurrency) is no longer supported, so your configuration files fail to parse. Such upgrades will be handled by LP: 1612517.

Thanks!
-Nish