The can_fail_404_links() test doesn't encounter a 404 response in
actuality, since the google.comys domain doesn't resolve. When the
test is updated such that the response's status code is a 404, the
test fails because the check_url() function doesn't handle
non-success responses how the test's assertions expect. This commit
updates check_url() to handle non-success responses, treating them
much like errors.
2f1b592ab4