I'm currently getting this error when running the maintenance/update.php script on my local MW installation.
Modifying exptime field of table objectcache ...Wikimedia\Rdbms\DBQueryError from line 1702 of /var/www/mediawiki/includes/libs/rdbms/database/Database.php: Error 1406: Data too long for column 'exptime' at row 1 (localhost)
Function: Wikimedia\Rdbms\Database::sourceFile( /var/www/mediawiki/maintenance/archives/patch-objectcache-exptime-notnull.sql )
Query: ALTER TABLE `objectcache`
MODIFY exptime BINARY(14) NOT NULL
#0 /var/www/mediawiki/includes/libs/rdbms/database/Database.php(1686): Wikimedia\Rdbms\Database->getQueryException('Data too long f...', 1406, 'ALTER TABLE `ob...', 'Wikimedia\\Rdbms...')
#1 /var/www/mediawiki/includes/libs/rdbms/database/Database.php(1661): Wikimedia\Rdbms\Database->getQueryExceptionAndLog('Data too long f...', 1406, 'ALTER TABLE `ob...', 'Wikimedia\\Rdbms...')
#2 /var/www/mediawiki/includes/libs/rdbms/database/Database.php(1230): Wikimedia\Rdbms\Database->reportQueryError('Data too long f...', 1406, 'ALTER TABLE `ob...', 'Wikimedia\\Rdbms...', false)
#3 /var/www/mediawiki/includes/libs/rdbms/database/Database.php(5125): Wikimedia\Rdbms\Database->query('ALTER TABLE `ob...', 'Wikimedia\\Rdbms...')
#4 /var/www/mediawiki/includes/libs/rdbms/database/Database.php(5060): Wikimedia\Rdbms\Database->sourceStream(Resource id #858, NULL, NULL, 'Wikimedia\\Rdbms...', NULL)
#5 /var/www/mediawiki/includes/libs/rdbms/database/DBConnRef.php(68): Wikimedia\Rdbms\Database->sourceFile('/var/www/mediaw...')
#6 /var/www/mediawiki/includes/libs/rdbms/database/MaintainableDBConnRef.php(35): Wikimedia\Rdbms\DBConnRef->__call('sourceFile', Array)
#7 /var/www/mediawiki/includes/installer/DatabaseUpdater.php(701): Wikimedia\Rdbms\MaintainableDBConnRef->sourceFile('/var/www/mediaw...')
#8 /var/www/mediawiki/includes/installer/DatabaseUpdater.php(1016): DatabaseUpdater->applyPatch('/var/www/mediaw...', false, 'Modifying expti...')
#9 /var/www/mediawiki/includes/installer/DatabaseUpdater.php(532): DatabaseUpdater->modifyField('objectcache', 'exptime', 'patch-objectcac...')
#10 /var/www/mediawiki/includes/installer/DatabaseUpdater.php(496): DatabaseUpdater->runUpdates(Array, false)
#11 /var/www/mediawiki/maintenance/update.php(182): DatabaseUpdater->doUpdates(Array)
#12 /var/www/mediawiki/maintenance/doMaintenance.php(106): UpdateMediaWiki->execute()
#13 /var/www/mediawiki/maintenance/update.php(253): require_once('/var/www/mediaw...')
#14 {main}$ php --version PHP 7.3.26-1+ubuntu18.04.1+deb.sury.org+1 (cli) (built: Jan 13 2021 08:00:44) ( NTS ) $ mysqld --version mysqld Ver 5.7.32-0ubuntu0.18.04.1 for Linux on x86_64 ((Ubuntu))