Possible unicode issues with validate_absolute_path

Hi, I caught this traceback info in my server logs:

    Uncaught exception GET /s/chat.html%E2%80%8F (**.**.**.**)
    HTTPServerRequest(protocol='http', host='www.****.com', method='GET', uri='/s/chat.html%E2%80%8F', version='HTTP/1.1', remote_ip='**.**.**.**', headers={'X-Real-Ip': '**.**.**.**, 'Accept-Language': 'he-IL,he;q=0.8,en-US;q=0.6,en;q=0.4', 'Host': 'www.****.com', 'Connection': 'upgrade', 'Upgrade-Insecure-Requests': '1', 'Accept': 'text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8', 'Accept-Encoding': 'gzip, deflate, sdch, br', 'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/53.0.2785.116 Safari/537.36'})
    Traceback (most recent call last):
        File "/home/production/.virtualenvs/wchat/lib/python3.5/site-packages/tornado/web.py", line 1445, in _execute
            result = yield result
        File "/home/production/.virtualenvs/wchat/lib/python3.5/site-packages/tornado/gen.py", line 1008, in run
            value = future.result()
        File "/home/production/.virtualenvs/wchat/lib/python3.5/site-packages/tornado/concurrent.py", line 232, in result
            raise_exc_info(self._exc_info)
        File "<string>", line 3, in raise_exc_info
        File "/home/production/.virtualenvs/wchat/lib/python3.5/site-packages/tornado/gen.py", line 282, in wrapper
            yielded = next(result)
        File "/home/production/.virtualenvs/wchat/lib/python3.5/site-packages/tornado/web.py", line 2265, in get
            self.root, absolute_path)
        File "/home/production/.virtualenvs/wchat/lib/python3.5/site-packages/tornado/web.py", line 2446, in validate_absolute_path
            if (os.path.isdir(absolute_path) and
        File "/home/production/.virtualenvs/wchat/lib/python3.5/genericpath.py", line 42, in isdir
            st = os.stat(s)
    UnicodeEncodeError: 'ascii' codec can't encode character '\u200f' in position 52: ordinal not in range(128)

(I removed the exact IP of the user and the domain names).
This error seems to happen every time I access the path /s/chat.html%E2%80%8F in my server. Note that this path (everything under /s) is server using web.StaticFileHandler.

I still haven't fully investigated this myself, though I was wondering if anyone had a similar problem. For reference, my installed Tornado version is 4.3. I am using python 3.5.1.

Start in tornado/web.py at StaticFileHandler and validate_absolute_path, using the reported /s/chat.html%E2%80%8F request and Python 3.5.1 environment to reproduce the traceback. Inspect how the percent-encoded path reaches os.path.isdir; done means the request no longer raises UnicodeEncodeError.