Python's os.path choking on Hebrew filenames

files = os.listdir('test_source')

for f in files:
    pf = os.path.join('test_source', f)
    print pf, os.path.exists(pf)

test_sourceex True
test_sourcejoe True
test_sourcemie.txt True
test_source__()'''.txt True
test_source????.txt False

files = os.listdir(u'test_source')

for f in files:

    pf = os.path.join(u'test_source', f)
    print pf.encode('ascii', 'replace'), os.path.exists(pf)

test_sourceex True
test_sourcejoe True
test_sourcemie.txt True
test_source__()'''.txt True
test_source????.txt True

subdir/bar.txt True
subdir/foo.txt True
subdir/עִבְרִית.txt True

for f in os.listdir(u'subdir'):
  pf = os.path.join(u'subdir', f)
  print pf, os.path.exists(pf)

subdir/bar.txt True
subdir/foo.txt True
subdir/עִבְרִית.txt True

>>>os.listdir(u'listdir')[2]
u'u05e2u05b4u05d1u05b0u05e8u05b4u05d9u05ea.txt'