19:59:51 1) FileImporter\Remote\MediaWiki\Test\ApiDetailRetrieverTest::testValidResponse with data set #0 (FileImporter\Data\SourceUrl Object (...), 'File:Foo.png', '{"query":{"pages":[{"title":"...}]}]}}', array('Foo.png', 'Foo', 'png')) 19:59:51 A non-numeric value encountered 19:59:51 19:59:51 /workspace/src/extensions/FileImporter/src/Remote/MediaWiki/ApiDetailRetriever.php:402 19:59:51 /workspace/src/extensions/FileImporter/src/Remote/MediaWiki/ApiDetailRetriever.php:225 19:59:51 /workspace/src/extensions/FileImporter/tests/phpunit/Remote/MediaWiki/ApiDetailRetrieverTest.php:431 19:59:51 /workspace/src/tests/phpunit/MediaWikiTestCase.php:416 19:59:51 /workspace/src/maintenance/doMaintenance.php:94 19:59:51 19:59:51 2) FileImporter\Remote\MediaWiki\Test\ApiDetailRetrieverTest::testValidResponse with data set #1 (FileImporter\Data\SourceUrl Object (...), 'Datei:Bar+1.JPG', '{"query":{"pages":[{"title":"...}]}]}}', array('Bar+1.JPG', 'Bar+1', 'JPG')) 19:59:51 A non-numeric value encountered 19:59:51 19:59:51 /workspace/src/extensions/FileImporter/src/Remote/MediaWiki/ApiDetailRetriever.php:402 19:59:51 /workspace/src/extensions/FileImporter/src/Remote/MediaWiki/ApiDetailRetriever.php:225 19:59:51 /workspace/src/extensions/FileImporter/tests/phpunit/Remote/MediaWiki/ApiDetailRetrieverTest.php:431 19:59:51 /workspace/src/tests/phpunit/MediaWikiTestCase.php:416 19:59:51 /workspace/src/maintenance/doMaintenance.php:94
https://integration.wikimedia.org/ci/job/quibble-vendor-mysql-php71-docker/166/consoleFull
You can comment "check experimental" to trigger PHP 7.1 tests to verify the fix.