'ascii' codec can't decode byte 0x89 in position 0: ordinal not in range(128)
2018-04-24 09:49:59,039 - telegram.ext.dispatcher - ERROR - An uncaught error was raised while processing the update
Traceback (most recent call last):
  File "C:\Python27\lib\site-packages\telegram\ext\dispatcher.py", line 279, in process_update
    handler.handle_update(update, self)
  File "C:\Python27\lib\site-packages\telegram\ext\commandhandler.py", line 173, in handle_update
    return self.callback(dispatcher.bot, update, **optional_args)
  File "bot_status.py", line 101, in graph_progress
    bot.send_photo(chat_id, open(photo, 'rb'))
  File "C:\Python27\lib\site-packages\telegram\bot.py", line 60, in decorator
    result = func(self, *args, **kwargs)
  File "C:\Python27\lib\site-packages\telegram\bot.py", line 85, in decorator
    result = self._request.post(url, data, timeout=kwargs.get('timeout'))
  File "C:\Python27\lib\site-packages\telegram\utils\request.py", line 270, in post
    'POST', url, body=data.to_form(), headers=data.headers, **urlopen_kwargs)
  File "C:\Python27\lib\site-packages\telegram\files\inputfile.py", line 127, in to_form
    return self._parse(form)
  File "C:\Python27\lib\site-packages\telegram\files\inputfile.py", line 141, in _parse
    return '\r\n'.join(form)
UnicodeDecodeError: 'ascii' codec can't decode byte 0x89 in position 0: ordinal not in range(128)

python-telegram-bot 10.0.2
certifi 2018.04.16
future 0.16.0
Python 2.7.14 (v2.7.14:84471935ed, Sep 16 2017, 20:25:58) [MSC v.1500 64 bit (AMD64)]