--kerberos option

[Giampaolo Lauria]

Hi Andrew,

I was wondering whether I could change the --kerberos credential option to 
be a boolean. Currently, it takes an argument which value could be in 
(yes,true,1,no, false,0). Also, what should the value of the kerberos 
state if the option is not specified?

Following is the code that handles the option:

def _set_kerberos(self, option, opt_str, arg, parser):
        if arg.lower() in ["yes", 'true', '1']:
            self.creds.set_kerberos_state(MUST_USE_KERBEROS)
        elif arg.lower() in ["no", 'false', '0']:
            self.creds.set_kerberos_state(DONT_USE_KERBEROS)
        else:
            raise optparse.BadOptionErr("invalid kerberos option: %s" % 
arg)

the option help says: "use kerberos", so why should the user specify a 
value? 
Also, optparse.BadOptionErr does not exist and specifying a value for this 
option other than the ones above causes an ugly error.

Thanks,
Giampaolo