In the PHPUnit tests, there is a collection of tests the check to ensure certain URLs don't validate, the tests is test_wp_http_validate_url_should_not_validate in tests/phpunit/tests/http/http.php. One is based on a URL presumed to not exist, however the URL is now registered and resolving to a website.

The address used currently is ​http://exampleeeee.com/caniload.php at line 552:
https://core.trac.wordpress.org/browser/trunk/tests/phpunit/tests/http/http.php#L552

Changing that URL, for example by adding another e in the domain will restore the test, although there may be a better solution.