werkzeug secure_filename fix python 3

gistfile1.txt

if isinstance(filename, text_type):
        from unicodedata import normalize
        filename = normalize('NFKD', filename).encode('ascii', 'ignore')
        
        if not PY2:
            filename = filename.decode('ascii')
            
    for sep in os.path.sep, os.path.altsep:
        if sep:
            filename = filename.replace(sep, ' ')
    filename = str(_filename_ascii_strip_re.sub('', '_'.join(
                   filename.split()))).strip('._')

    # on nt a couple of special files are present in each folder.  We
    # have to ensure that the target file is not such a filename.  In
    # this case we prepend an underline
    if os.name == 'nt' and filename and \
       filename.split('.')[0].upper() in _windows_device_files:
        filename = '_' + filename

    return filename