Comment 2 for bug 743359

I also got similar error lasting;
Apr 3 13:43:19 ubuntu finish-install: Disabling CD in sources.list
Apr 3 13:43:19 ubuntu python: Exception during installation:
Apr 3 13:43:19 ubuntu python: Traceback (most recent call last):
Apr 3 13:43:19 ubuntu python: File "/usr/share/ubiquity/plugininstall.py", line 1424, in <module>
Apr 3 13:43:19 ubuntu python: install.run()
Apr 3 13:43:19 ubuntu python: File "/usr/share/ubiquity/plugininstall.py", line 54, in wrapper
Apr 3 13:43:19 ubuntu python: func(self)
Apr 3 13:43:19 ubuntu python: File "/usr/share/ubiquity/plugininstall.py", line 187, in run
Apr 3 13:43:19 ubuntu python: self.remove_extras()
Apr 3 13:43:19 ubuntu python: File "/usr/share/ubiquity/plugininstall.py", line 1214, in remove_extras
Apr 3 13:43:19 ubuntu python: self.do_remove(regular)
Apr 3 13:43:19 ubuntu python: File "/usr/share/ubiquity/plugininstall.py", line 871, in do_remove
Apr 3 13:43:19 ubuntu python: if not cache.commit(fetchprogress, installprogress):
Apr 3 13:43:19 ubuntu python: File "/usr/lib/python2.6/dist-packages/apt/deprecation.py", line 98, in deprecated_function
Apr 3 13:43:19 ubuntu python: return func(*args, **kwds)
Apr 3 13:43:19 ubuntu python: File "/usr/lib/python2.6/dist-packages/apt/cache.py", line 424, in commit
Apr 3 13:43:19 ubuntu python: res = self._fetch_archives(fetcher, pm)
Apr 3 13:43:19 ubuntu python: File "/usr/lib/python2.6/dist-packages/apt/cache.py", line 271, in _fetch_archives
Apr 3 13:43:19 ubuntu python: raise LockFailedException("Failed to lock %s" % lockfile)
Apr 3 13:43:19 ubuntu python: LockFailedException: Failed to lock /target/var/cache/apt/archives/lock
Apr 3 13:43:19 ubuntu python: