Fix vcs-import of archlinux-lp

The import doesn't work, see https://code.launchpad.net/~vcs-imports/archlinux-lp/mirror

And the error:
Traceback (most recent call last):
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/scripts/../scripts/code-import-worker.py", line 46, in ?
    script.main()
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/scripts/../scripts/code-import-worker.py", line 41, in main
    import_worker.run()
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/utilities/../lib/canonical/codehosting/codeimport/worker.py", line 372, in run
    self.importToBazaar(foreign_tree, bazaar_tree)
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/utilities/../lib/canonical/codehosting/codeimport/worker.py", line 314, in importToBazaar
    self._runToBaz(
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/utilities/../lib/canonical/codehosting/codeimport/worker.py", line 340, in _runToBaz
    totla.totla(config, self._logger, config.args, SCM.tree(source_dir))
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/utilities/../lib/cscvs/cmds/totla.py", line 229, in totla
    apply.rangeParser = source_tree.changesetRangeParser(
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/scripts/../lib/svn_oo/WorkingTree.py", line 80, in changesetRangeParser
    parser = RevisionRangeParser(
  File "/srv/importd.launchpad.net/production/launchpad-rev-7322/scripts/../lib/svn_oo/WorkingTree.py", line 111, in reporelpath
    raise LookupError("Cannot find svn repository root")
LookupError: Cannot find svn repository root
Import failed:
Traceback (most recent call last):
Failure: twisted.internet.error.ProcessTerminated: A process has ended with a probable error condition: process ended with exit code 1.