Comment 4 for bug 786096

Exception during installation:
May 21 08:44:57 ubuntu plugininstall.py: Traceback (most recent call last):
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 1547, in <module>
May 21 08:44:57 ubuntu plugininstall.py: install.run()
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 56, in wrapper
May 21 08:44:57 ubuntu plugininstall.py: func(self)
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 208, in run
May 21 08:44:57 ubuntu plugininstall.py: self.remove_extras()
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 1303, in remove_extras
May 21 08:44:57 ubuntu plugininstall.py: self.do_remove(regular)
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/share/ubiquity/plugininstall.py", line 923, in do_remove
May 21 08:44:57 ubuntu plugininstall.py: if not cache.commit(fetchprogress, installprogress):
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/lib/python2.7/dist-packages/apt/deprecation.py", line 98, in deprecated_function
May 21 08:44:57 ubuntu plugininstall.py: return func(*args, **kwds)
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 433, in commit
May 21 08:44:57 ubuntu plugininstall.py: res = self._fetch_archives(fetcher, pm)
May 21 08:44:57 ubuntu plugininstall.py: File "/usr/lib/python2.7/dist-packages/apt/cache.py", line 279, in _fetch_archives
May 21 08:44:57 ubuntu plugininstall.py: raise LockFailedException("Failed to lock %s" % lockfile)
May 21 08:44:57 ubuntu plugininstall.py: LockFailedException: Failed to lock /target/var/cache/apt/archives/lock
May 21 08:44:57 ubuntu plugininstall.py: