`@!has` (and `@!matches`) with two arguments used to treat the second
argument as a literal string of HTML code. Now, that feature has been
renamed into `@!hasraw` (and `@!matchesraw`), and the arity-2 `@!has`
version is an error.
These uses thought the second argument was being treated as an XPath, as
with the arity-3 version, but in fact was being treated as literal HTML.
Because these were checking for the *absence* of the string, the tests
silently did nothing -- an XPath string won't ever be showing up in the
test's generated HTML!
The command is `@!has`, not `!@has`. I don't think these checks were
doing anything before! Ideally we would accept `!@has` as well, or at
least fail tests that use `!@has`. The current behavior seems to be
silently ignoring the check, which is very confusing.
