def __read_master_key(self):
        '''
        Read in the rotating master authentication key
        '''
        key_user = self.salt_user
        if key_user == 'root':
            if self.opts.get('user', 'root') != 'root':
                key_user = self.opts.get('user', 'root')
        if key_user.startswith('sudo_'):
            key_user = self.opts.get('user', 'root')
        keyfile = os.path.join(self.opts['cachedir'],
                               '.{0}_key'.format(key_user))
        # Make sure all key parent directories are accessible
        salt.utils.verify.check_path_traversal(self.opts['cachedir'],
                                               key_user,
                                               self.skip_perm_errors)

        try:
            with salt.utils.fopen(keyfile, 'r') as key:
                return key.read()
        except (OSError, __HOLE__):
            # Fall back to eauth
            return ''
dataset/ETHPy150Open saltstack/salt/salt/client/__init__.py/LocalClient.__read_master_key