WorkingTree4._iter_changes traverses unversioned directories

In bzr.dev, WorkingTree4._iter_changes traverses unversioned subdirectories. This has bad behavior implications and bad performance implications.

Behavior: The user may not have permission to traverse the unversioned subdirectories. This causes a Permission denied error. This does not occur with WorkingTree3.

Performance: If the unversioned part of the tree is large, Bazaar may spend significant time traversing the unversioned directory. This performance penalty is not necessary: since the directories are unversioned, they can produce no useful information.

abentley@balrog:~/wrelease$ bzr status -Derror M forms2.r7-6-3/clerkrespond.html
 M forms2.r7-6-3/custom/gcl-top-survey.html
 M forms2.r7-6-3/custom/gcl-top.html
 M forms2.r7-6-3/custom/gqi-top.html
 M forms2.r7-6-3/survey/getorg.xml
+N forms2.r7-6-3/survey/intro.html
+N forms2.r7-6-3/survey/intro.xml
bzr: ERROR: exceptions.OSError: [Errno 13] Permission denied: '/home/abentley/configs/web//forms2.r7-6-3/tmp/ziptempAp5BkA'

Traceback (most recent call last):
  File "/home/abentley/bzr/bzr.dev/bzrlib/commands.py", line 638, in run_bzr_catch_errors
    return run_bzr(argv)
  File "/home/abentley/bzr/bzr.dev/bzrlib/commands.py", line 600, in run_bzr
    ret = run(*run_argv)
  File "/home/abentley/bzr/bzr.dev/bzrlib/commands.py", line 296, in run_argv_aliases
    return self.run(**all_cmd_args)
  File "/home/abentley/bzr/bzr.dev/bzrlib/commands.py", line 610, in ignore_pipe
    result = func(*args, **kwargs)
  File "/home/abentley/bzr/bzr.dev/bzrlib/builtins.py", line 202, in run
    to_file=self.outf, short=short, versioned=versioned)
  File "/home/abentley/bzr/bzr.dev/bzrlib/status.py", line 153, in show_tree_status
    _mod_delta.report_changes(changes, reporter)
  File "/home/abentley/bzr/bzr.dev/bzrlib/delta.py", line 390, in report_changes
    for (file_id, path, content_change, versioned, parent_id, name, kind,
  File "/home/abentley/bzr/bzr.dev/bzrlib/workingtree_4.py", line 2123, in _iter_changes
    current_dir_info = dir_iterator.next()
  File "/home/abentley/bzr/bzr.dev/bzrlib/osutils.py", line 1216, in _walkdirs_unicode_to_utf8
    for name in sorted(_listdir(top)):
OSError: [Errno 13] Permission denied: '/home/abentley/configs/web//forms2.r7-6-3/tmp/ziptempAp5BkA'

bzr 0.16.0dev0 on python 2.4.1.final.0 (linux2)
arguments: ['/home/abentley/bin/bzr', 'status', '-Derror']

** please send this report to <email address hidden>