RFC 3454 says about prohibited characters (section 2, "Preparation
Overview"):
3) Prohibit -- Check for any characters that are not allowed in the
output. If any are found, return an error. This is described in
section 5.
In other words, we mustn't simply strip the output of prohibited
characters. We must generate an error if they are present. We do that by
clearing the data.
We already had tests for prohibited output, but they were
indistinguishable from being stripped. So instead add some extra
characters so that we can tell whether the label was cleared.
Change-Id: I2d95217c27be5e2d54deed0036cb009e3b7f4886
Reviewed-by: Konstantin Ritt <ritt.ks@gmail.com>
736a052d93