package mysql-server-5.7 5.7.25-0ubuntu0.16.04.2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1

[Eduardo Moya Quiroz]

the system was started normally without any human interaction after logon.

ProblemType: Package
DistroRelease: Ubuntu 16.04
Package: mysql-server-5.7 5.7.25-0ubuntu0.16.04.2
ProcVersionSignature: Ubuntu 4.15.0-43.46~16.04.1-generic 4.15.18
Uname: Linux 4.15.0-43-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.18
Architecture: amd64
Date: Thu Jan 24 09:53:10 2019
ErrorMessage: subprocess installed post-installation script returned error exit status 1
InstallationDate: Installed on 2018-02-27 (330 days ago)
InstallationMedia: Ubuntu-MATE 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
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: ['sys', 'ib_buffer_pool', 'auto.cnf', 'debian-5.7.flag', 'mysql', 'ibdata1', 'ib_logfile1', 'ib_logfile0', 'sernameg_planificacion', 'performance_schema', 'abaciocco']
ProcCmdline: BOOT_IMAGE=/vmlinuz-4.15.0-43-generic root=/dev/mapper/ubuntu--mate--vg-root ro quiet splash
RelatedPackageVersions:
 dpkg 1.18.4ubuntu1.5
 apt 1.2.29ubuntu0.1
SourcePackage: mysql-5.7
Title: package mysql-server-5.7 5.7.25-0ubuntu0.16.04.2 failed to install/upgrade: subprocess installed post-installation script returned error exit status 1
UpgradeStatus: No upgrade log present (probably fresh install)
upstart.mysql.override: manual

[Launchpad Janitor (janitor)]

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

[Christian Ehrhardt  (paelzer)]

Hi,
this was properly triggered by an update running in background.
It is a known issue and I'll dup you onto the main bug for it.

TL;DR: a race makes mysql not available, so on the update when it is restarted the postinst fails to connect