'Changes directory to the expanded archive directory.
Dies with an error if there was no expanded archive.'

def chdir_to_source(self):

    path = self.source_path
    if (not path):
        raise StageError('Attempt    to    chdir    before    expanding    archive.')
    else:
        os.chdir(path)
        if (not os.listdir(path)):
            raise StageError(('Archive    was    empty    for    %s' % self.name))
