An empty patch (https://gerrit.wikimedia.org/r/c/mediawiki/core/+/749876) failed with the following error.
12:49:13 There was 1 failure: 12:49:13 12:49:13 1) MessageCacheTest::testMessageFallbacks with data set #4 ('sunday', 'ab', 'амҽыш') 12:49:13 Message fallback failed. 12:49:13 Failed asserting that two strings are equal. 12:49:13 --- Expected 12:49:13 +++ Actual 12:49:13 @@ @@ 12:49:13 -'амҽыш' 12:49:13 +'Амҽыша' 12:49:13 12:49:13 /workspace/src/tests/phpunit/includes/cache/MessageCacheTest.php:94 12:49:13 /workspace/src/tests/phpunit/MediaWikiIntegrationTestCase.php:452