IPSet tests fail on PHP 7.3:
22:32:18 1) Wikimedia\IPSet\Test\IPSetTest::testAddCidrWarning with data set "inet fail" ('0af.0af')
22:32:18 Failed asserting that exception of type "PHPUnit\Framework\Error\Warning" is thrown.
22:32:18
22:32:18 2) Wikimedia\IPSet\Test\IPSetTest::testMatchWarning with data set "inet fail" ('0af.0af', false)
22:32:18 Failed asserting that exception of type "PHPUnit\Framework\Error\Warning" is thrown.
https://integration.wikimedia.org/ci/job/composer-package-php73-docker/13/console
cc @BBlack as the primary author.