Comment 3 for bug 1168864

From the log file it looks like you actually were installing over an existing Precise install and there was a crash in apt-clone:

Apr 14 11:58:44 ubuntu ubiquity: Traceback (most recent call last):
Apr 14 11:58:44 ubuntu ubiquity: File "/usr/bin/apt-clone", line 117, in <module>
Apr 14 11:58:44 ubuntu ubiquity: args.source, args.destination, args.new_distro_codename, protect_installed)
Apr 14 11:58:44 ubuntu ubiquity: File "/usr/lib/python2.7/dist-packages/apt_clone.py", line 327, in restore_state
Apr 14 11:58:44 ubuntu ubiquity: self._restore_sources_list(statefile, targetdir)
Apr 14 11:58:44 ubuntu ubiquity: File "/usr/lib/python2.7/dist-packages/apt_clone.py", line 366, in _restore_sources_list
Apr 14 11:58:44 ubuntu ubiquity: tar.extract(self.TARPREFIX+"etc/apt/sources.list", targetdir)
Apr 14 11:58:44 ubuntu ubiquity: File "/usr/lib/python2.7/tarfile.py", line 2076, in extract
Apr 14 11:58:44 ubuntu ubiquity: tarinfo = self.getmember(member)
Apr 14 11:58:44 ubuntu ubiquity: File "/usr/lib/python2.7/tarfile.py", line 1796, in getmember
Apr 14 11:58:44 ubuntu ubiquity: raise KeyError("filename %r not found" % name)
Apr 14 11:58:44 ubuntu ubiquity: KeyError: "filename './etc/apt/sources.list' not found"