package mysql-server-5.7 5.7.11-0ubuntu6 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Václav Haisman]

It broke my upgrade process from Wily.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: mysql-server-5.7 5.7.11-0ubuntu6
ProcVersionSignature: Ubuntu 4.2.0-23.28-lowlatency 4.2.6
Uname: Linux 4.2.0-23-lowlatency x86_64
ApportVersion: 2.20.1-0ubuntu2
Architecture: amd64
Date: Sat Apr 23 05:39:49 2016
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2011-11-13 (1622 days ago)
InstallationMedia: Xubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
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: ['mythconverg', 'test', 'mysql', 'auto.cnf', 'mysql_upgrade_info', 'debian-5.6.flag', 'debian-5.5.flag', 'ibdata1', 'performance_schema', 'debian-5.7.flag', 'ib_logfile1', 'ib_logfile0', 'ib_buffer_pool']
ProcCmdline: BOOT_IMAGE=/boot/vmlinuz-4.2.0-23-lowlatency root=UUID=503b3cdd-770e-4354-bf3d-c917a2ebe292 ro nomdmonddf nomdmonisw nomdmonddf nomdmonisw elevator=cfq nomdmonddf nomdmonisw nomdmonddf nomdmonisw
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1
 apt 1.2.10ubuntu1
SourcePackage: mysql-5.7
Title: package mysql-server-5.7 5.7.11-0ubuntu6 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: Upgraded to xenial on 2016-04-23 (0 days ago)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.