I am running importDump.php to import Wiktionary into a local MediaWiki instance (XAMPP on Windows 10).
This error occurs when the importer reaches the attached example.xml page:
C:\xampp\htdocs\mediawiki-134git\maintenance>php importDump.php --conf ../LocalSettings.php --username-prefix="" C:\example.xml Wikimedia\Rdbms\DBUnexpectedError from line 3880 of C:\xampp\htdocs\mediawiki-134git\includes\libs\rdbms\database\Database.php: No atomic section is open (got MediaWiki\Revision\RevisionStore::insertRevisionOn) #0 C:\xampp\htdocs\mediawiki-134git\includes\libs\rdbms\database\Database.php(3968): Wikimedia\Rdbms\Database->cancelAtomic('MediaWiki\\Revis...', Object(Wikimedia\Rdbms\AtomicSectionIdentifier)) #1 C:\xampp\htdocs\mediawiki-134git\includes\libs\rdbms\database\DBConnRef.php(68): Wikimedia\Rdbms\Database->doAtomicSection('MediaWiki\\Revis...', Object(Closure)) #2 C:\xampp\htdocs\mediawiki-134git\includes\libs\rdbms\database\DBConnRef.php(635): Wikimedia\Rdbms\DBConnRef->__call('doAtomicSection', Array) #3 C:\xampp\htdocs\mediawiki-134git\includes\Revision\RevisionStore.php(498): Wikimedia\Rdbms\DBConnRef->doAtomicSection('MediaWiki\\Revis...', Object(Closure)) #4 C:\xampp\htdocs\mediawiki-134git\includes\Revision.php(968): MediaWiki\Revision\RevisionStore->insertRevisionOn(Object(MediaWiki\Revision\MutableRevisionRecord), Object(Wikimedia\Rdbms\DBConnRef)) #5 C:\xampp\htdocs\mediawiki-134git\includes\import\ImportableOldRevisionImporter.php(129): Revision->insertOn(Object(Wikimedia\Rdbms\DBConnRef)) #6 C:\xampp\htdocs\mediawiki-134git\includes\import\WikiRevision.php(616): ImportableOldRevisionImporter->import(Object(WikiRevision)) #7 C:\xampp\htdocs\mediawiki-134git\includes\import\WikiImporter.php(366): WikiRevision->importOldRevision() #8 C:\xampp\htdocs\mediawiki-134git\maintenance\importDump.php(209): WikiImporter->importRevision(Object(WikiRevision)) #9 C:\xampp\htdocs\mediawiki-134git\includes\import\WikiImporter.php(501): BackupReader->handleRevision(Object(WikiRevision), Object(WikiImporter)) #10 C:\xampp\htdocs\mediawiki-134git\includes\import\WikiImporter.php(941): WikiImporter->revisionCallback(Object(WikiRevision)) #11 C:\xampp\htdocs\mediawiki-134git\includes\import\WikiImporter.php(860): WikiImporter->processRevision(Array, Array) #12 C:\xampp\htdocs\mediawiki-134git\includes\import\WikiImporter.php(802): WikiImporter->handleRevision(Array) #13 C:\xampp\htdocs\mediawiki-134git\includes\import\WikiImporter.php(606): WikiImporter->handlePage() #14 C:\xampp\htdocs\mediawiki-134git\maintenance\importDump.php(359): WikiImporter->doImport() #15 C:\xampp\htdocs\mediawiki-134git\maintenance\importDump.php(292): BackupReader->importFromHandle(Resource id #160) #16 C:\xampp\htdocs\mediawiki-134git\maintenance\importDump.php(127): BackupReader->importFromFile('C:\\Users\\Brenda...') #17 C:\xampp\htdocs\mediawiki-134git\maintenance\doMaintenance.php(99): BackupReader->execute() #18 C:\xampp\htdocs\mediawiki-134git\maintenance\importDump.php(364): require_once('C:\\xampp\\htdocs...') #19 {main}