test_external_diffest_external_diff fails when run with py2exe build

This depends on whether or not it can find a "diff" program to run. If you have one it passes, if you don't it fails. Regardless of the standalone installer or not.

What is really weird is that on my machine I get:
$ bzr selftest -s bb.test_diff.TestExternalDiff
bzr selftest: C:/Users/jameinel/dev/bzr/bzr.dev/bzr
   C:\Users\jameinel\dev\bzr\bzr.dev\bzrlib
   bzr-2.3.0dev4 python-2.6.4 Windows-Vista-6.0.6002-SP2

----------------------------------------------------------------------
Ran 2 tests in 4.352s

OK
Missing feature 'diff executable' skipped 1 tests.

Which says that it does check for "diff" being runnable and skips the test. So the real question is why does it think you have a 'diff' that it can run, but it fails to run it.

I hit this too running selftest under wine:

Traceback (most recent call last):
  File "Z:\home\mbp\lib\python\testtools\runtest.py", line 144, in _run_user
    return fn(*args)
  File "Z:\home\mbp\lib\python\testtools\testcase.py", line 465, in _run_test_method
    testMethod()
  File "Z:\home\mbp\bzr\trunk\bzrlib\tests\blackbox\test_diff.py", line 398, in test_external_diff
    self.assertEqual('', err)
AssertionError: not equal:
a = ''
b = 'bzr: ERROR: [Error 2] File not found\n'

There is another, possibly similar, failure:

Traceback (most recent call last):
  File "Z:\home\mbp\lib\python\testtools\runtest.py", line 144, in _run_user
    return fn(*args)
  File "Z:\home\mbp\lib\python\testtools\testcase.py", line 465, in _run_test_method
    testMethod()
  File "Z:\home\mbp\bzr\trunk\bzrlib\tests\per_merger.py", line 343, in test_can_access_this_other_and_base_versions
    conflicts = builder.merge(self.merge_type)
  File "Z:\home\mbp\bzr\trunk\bzrlib\tests\test_merge_core.py", line 80, in merge
    merger.do_merge()
  File "Z:\home\mbp\bzr\trunk\bzrlib\merge.py", line 830, in do_merge
    operation.run()
  File "Z:\home\mbp\bzr\trunk\bzrlib\cleanup.py", line 131, in run
    self.cleanups, self.func, self, *args, **kwargs)
  File "Z:\home\mbp\bzr\trunk\bzrlib\cleanup.py", line 165, in _do_with_cleanups
    result = func(*args, **kwargs)
  File "Z:\home\mbp\bzr\trunk\bzrlib\merge.py", line 835, in _do_merge
    self._compute_transform()
  File "Z:\home\mbp\bzr\trunk\bzrlib\merge.py", line 873, in _compute_transform
    file_status = self._do_merge_contents(file_id)
  File "Z:\home\mbp\bzr\trunk\bzrlib\merge.py", line 1377, in _do_merge_contents
    hook_status, lines = hook.merge_contents(params)
  File "Z:\home\mbp\bzr\trunk\bzrlib\merge.py", line 1465, in merge_contents
    merge_hook_params.trans_id)
  File "Z:\home\mbp\bzr\trunk\bzrlib\merge.py", line 1750, in text_merge
    status = bzrlib.patch.diff3(new_file, this, base, other)
  File "Z:\home\mbp\bzr\trunk\bzrlib\patch.py", line 93, in diff3
    raise NoDiff3
NoDiff3: Diff3 is not installed on this machine.