no support for filenames containing unicode (Hebrew in my case)

[eyal-rounds]

Traceback (most recent call last):
  File "duplicate_finder.py", line 358, in <module>
    add(args['<path>'], db)
  File "duplicate_finder.py", line 194, in add
    for result in hash_files_parallel(files):
  File "duplicate_finder.py", line 159, in hash_files_parallel
    for result in executor.map(hash_file, files):
  File "/usr/lib/python3.5/concurrent/futures/process.py", line 484, in map
    timeout=timeout)
  File "/usr/lib/python3.5/concurrent/futures/_base.py", line 548, in map
    fs = [self.submit(fn, *args) for args in zip(*iterables)]
  File "/usr/lib/python3.5/concurrent/futures/_base.py", line 548, in <listcomp>
    fs = [self.submit(fn, *args) for args in zip(*iterables)]
  File "/usr/lib/python3.5/concurrent/futures/process.py", line 139, in _get_chunks
    chunk = tuple(itertools.islice(it, chunksize))
  File "duplicate_finder.py", line 182, in new_image_files
    if _in_database(file, db):
  File "duplicate_finder.py", line 177, in _in_database
    return db.count({"_id": file}) > 0
  File "/usr/local/lib/python3.5/dist-packages/pymongo/collection.py", line 1560, in count
    return self._count(cmd, collation, session)
  File "/usr/local/lib/python3.5/dist-packages/pymongo/collection.py", line 1511, in _count
    session=session)
  File "/usr/local/lib/python3.5/dist-packages/pymongo/collection.py", line 245, in _command
    retryable_write=retryable_write)
  File "/usr/local/lib/python3.5/dist-packages/pymongo/pool.py", line 522, in command
    self._raise_connection_failure(error)
  File "/usr/local/lib/python3.5/dist-packages/pymongo/pool.py", line 677, in _raise_connection_failure
    raise error
  File "/usr/local/lib/python3.5/dist-packages/pymongo/pool.py", line 517, in command
    collation=collation)
  File "/usr/local/lib/python3.5/dist-packages/pymongo/network.py", line 103, in command
    None, codec_options, check_keys)
UnicodeEncodeError: 'utf-8' codec can't encode character '\udcd7' in position 49: surrogates not allowed

making some printing seems like there is a file with a name in hebrew (unicode):

#### CodecOptions(document_class=dict, tz_aware=False, uuid_representation=PYTHON_LEGACY, unicode_decode_error_handler='replace', tzinfo=None) 4 image_database.$cmd SON([('count', 'images'), ('query', {'_id': "/home/cmp/all_our_pics/15-04-2017 Maytal's phone/\udcd7\udc9e\udcd7\udca1\udcd7\udc9e\udcd7\udc9b\udcd7\udc99\udcd7\udc9d/20151015_130430.jpg"}), ('lsid', {'id': Binary(b'\x8c&\xf7\x96\xcf\xf0OZ\xb95\xaaf+\xd2\x91\x98', 4)})]) False```

the printing line: ```print("####", str(codec_options), str(flags), str(ns), str(spec), str(check_keys))```
was added to: 
/usr/local/lib/python3.5/dist-packages/pymongo/network.py
line 101.

As you can see the "undecodable" char is unicode but i *CAN* be encoeded as utf-8 using python. was done by my scripts in the past. Not sure what the issue here is.