@code{arith-error}. The @code{:type} argument to @code{should-error}
is optional; if absent, any type of error is accepted.
@code{should-error} returns an error description of the error that was
-signalled, to allow additional checks to be made. The error
+signaled, to allow additional checks to be made. The error
description has the format @code{(ERROR-SYMBOL . DATA)}.
There is no @code{should-not-error} macro since tests that signal an