11.04通过iso不能升级

[pinna_angel]

下载了oneiric-alternate-amd64.iso，mount到一个目录后，执行升级命令后产生最后那样的错误，什么原因，下载的文件产生问题了？
./cdromupgrade
WARNING: Failed to read mirror file
gpgv: 于 2011年10月11日 星期二 20时44分15秒 CST 创建的签名，使用 DSA，钥匙号 FBB75451
gpgv: 完好的签名，来自于“Ubuntu CD Image Automatic Signing Key <[email protected]>”
Traceback (most recent call last):
File "/tmp/tmp.F0F0wdFKrf/oneiric", line 7, in <module>
sys.exit(main())
File "/tmp/tmp.F0F0wdFKrf/DistUpgradeMain.py", line 199, in main
if app.run():
File "/tmp/tmp.F0F0wdFKrf/DistUpgradeController.py", line 1670, in run
return self.fullUpgrade()
File "/tmp/tmp.F0F0wdFKrf/DistUpgradeController.py", line 1627, in fullUpgrade
if not self.askDistUpgrade():
File "/tmp/tmp.F0F0wdFKrf/DistUpgradeController.py", line 895, in askDistUpgrade
if not self._checkFreeSpace():
File "/tmp/tmp.F0F0wdFKrf/DistUpgradeController.py", line 861, in _checkFreeSpace
with_snapshots = self._is_apt_btrfs_snapshot_supported()
File "/tmp/tmp.F0F0wdFKrf/DistUpgradeController.py", line 1005, in _is_apt_btrfs_snapshot_supported
apt_btrfs = apt_btrfs_snapshot.AptBtrfsSnapshot()
File "/tmp/tmp.F0F0wdFKrf/apt_btrfs_snapshot.py", line 85, in __init__
self.fstab = Fstab(fstab)
File "/tmp/tmp.F0F0wdFKrf/apt_btrfs_snapshot.py", line 53, in __init__
entry = FstabEntry.from_line(line)
File "/tmp/tmp.F0F0wdFKrf/apt_btrfs_snapshot.py", line 31, in from_line
return FstabEntry(*line.split())
TypeError: __init__() takes at most 7 arguments (8 given)

[pinna_angel]

没有人解答一下呀。