Oneiric Ocelot installer failure

Running the daily desktop build of the not-yet-released Ubuntu Oneiric (11.10), I kept getting install failures. /var/log/syslog showed that the problem was in /usr/share/ubiquity/install.py line 372. It was failing because the unlink / readlink / symlink wasn't working on /var/run and /var/lock.

Editing it as root, I changed it to:

try:
  os.unlink(targetpath)
except:
  print "Can't unlink " + targetpath

And:

try:
  linkto = os.readlink(sourcepath)
  os.symlink(linkto, targetpath)
except:
  print "symlink " + sourcepath + linkto + targetpath

And then it seemed to work.