Empty return and error for UTF8 (surrogate) filename.

[1mm0rt41PC]

I have files with french charset on Windows.
Some of them are encoded in the modified utf8 => https://stackoverflow.com/questions/51001150/what-are-surrogate-characters-in-utf-8

By default, surrogate escaping is not enabled and any request with a filename with "Modified UTF8" encoding will crash :

10:21:11.254 - <1729885280> wsgidav.wsgidav_app         INFO    : 127.0.0.1 - 1mm0rt41 - [2020-04-15 08:21:11] "PROPFIND /home/desktop.ini" length=0, depth=0, elap=0.001sec -> 404 Not Found
10:21:13.980 - <1721496672> wsgidav.error_printer       ERROR   : Caught Exception
Traceback (most recent call last):
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/error_printer.py", line 52, in __call__
    for v in app_iter:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/request_resolver.py", line 213, in __call__
    for v in app_iter:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/request_server.py", line 126, in __call__
    app_iter = provider.custom_request_handler(environ, start_response, method)
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/dav_provider.py", line 1525, in custom_request_handler
    return default_handler(environ, start_response)
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/request_server.py", line 355, in do_PROPFIND
    propList = child.get_properties("allprop")
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/dav_provider.py", line 560, in get_properties
    name_list = self.get_property_names(mode == "allprop")
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/dav_provider.py", line 518, in get_property_names
    if self.get_etag() is not None:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/fs_dav_provider.py", line 66, in get_etag
    return util.get_etag(self._file_path)
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/util.py", line 973, in get_etag
    file_path = file_path.encode("utf8")
UnicodeEncodeError: 'utf-8' codec can't encode character '\udcc3' in position 61: surrogates not allowed

ValueError("invalid literal for int() with base 10: ''",)
Traceback (most recent call last):
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/cheroot/wsgi.py", line 145, in respond
    for chunk in filter(None, response):
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/wsgidav_app.py", line 563, in __call__
    for v in app_iter:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/debug_filter.py", line 157, in __call__
    for v in app_iter:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/error_printer.py", line 52, in __call__
    for v in app_iter:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/request_resolver.py", line 213, in __call__
    for v in app_iter:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/request_server.py", line 126, in __call__
    app_iter = provider.custom_request_handler(environ, start_response, method)
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/dav_provider.py", line 1525, in custom_request_handler
    return default_handler(environ, start_response)
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/request_server.py", line 355, in do_PROPFIND
    propList = child.get_properties("allprop")
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/dav_provider.py", line 560, in get_properties
    name_list = self.get_property_names(mode == "allprop")
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/dav_provider.py", line 518, in get_property_names
    if self.get_etag() is not None:
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/fs_dav_provider.py", line 66, in get_etag
    return util.get_etag(self._file_path)
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/wsgidav/util.py", line 973, in get_etag
    file_path = file_path.encode("utf8")
UnicodeEncodeError: 'utf-8' codec can't encode character '\udcc3' in position 61: surrogates not allowed

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/cheroot/server.py", line 1269, in communicate
    req.respond()
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/cheroot/server.py", line 1071, in respond
    self.server.gateway(self).respond()
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/cheroot/wsgi.py", line 151, in respond
    self.req.ensure_headers_sent()
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/cheroot/server.py", line 1118, in ensure_headers_sent
    self.send_headers()
  File "/volume1/@appstore/py3k/usr/local/lib/python3.5/site-packages/cheroot/server.py", line 1136, in send_headers
    status = int(self.status[:3])

The fix is easy, just change the line 973 in the file "wsgidav/util.py"
from:

file_path = file_path.encode("utf8")

to

file_path = file_path.encode("utf8","surrogateescape")