[qmtest] derivation issues?

[eichin at metacarta.com]

Today's problem: how does one set argument values in parent classes
correctly?  In particular, I've got something derived from
ShellScriptTest that runs a find [and does some other things with
arguments, so it isn't just an instance, it is a new class of test.]

I can just set self.script in the the Run method, before calling the
parent Run... but I'd really like to, for example, set Hidden on that
argument, or at least set the default_value to my find command so that
the user sees it.  Thoughts?