'Given a become_method, set the privilege escalation method when using become'

def do_become_method(self, arg):

    if arg:
        self.options.become_method = arg
        display.v(('become_method    changed    to    %s' % self.options.become_method))
    else:
        display.display('Please    specify    a    become_method,    e.g.    `become_method    su`')
