Null characters breaking CSV reading

[drkane]

2019-11-01T10:55:19.197118897Z app[web.1]: Traceback (most recent call last):
2019-11-01T10:55:19.197158960Z app[web.1]:   File "/app/.heroku/python/bin/bottle.py", line 862, in _handle
2019-11-01T10:55:19.197164779Z app[web.1]:     return route.call(**args)
2019-11-01T10:55:19.197168502Z app[web.1]:   File "/app/.heroku/python/bin/bottle.py", line 1740, in wrapper
2019-11-01T10:55:19.197172380Z app[web.1]:     rv = callback(*a, **ka)
2019-11-01T10:55:19.197176020Z app[web.1]:   File "/app/server.py", line 217, in add_to_csv
2019-11-01T10:55:19.197179797Z app[web.1]:     process_csv(codecs.iterdecode(upload.file, 'utf-8'), output, app.config, column_name, fields)
2019-11-01T10:55:19.197183613Z app[web.1]:   File "/app/process_csv.py", line 27, in process_csv
2019-11-01T10:55:19.197187031Z app[web.1]:     for _, row in enumerate(reader):
2019-11-01T10:55:19.197190702Z app[web.1]:   File "/app/.heroku/python/lib/python3.6/csv.py", line 112, in __next__
2019-11-01T10:55:19.197194384Z app[web.1]:     row = next(self.reader)
2019-11-01T10:55:19.197197628Z app[web.1]:   File "/app/.heroku/python/lib/python3.6/codecs.py", line 1039, in iterdecode
2019-11-01T10:55:19.197201342Z app[web.1]:     output = decoder.decode(input)
2019-11-01T10:55:19.197204573Z app[web.1]:   File "/app/.heroku/python/lib/python3.6/codecs.py", line 321, in decode
2019-11-01T10:55:19.197208220Z app[web.1]:     (result, consumed) = self._buffer_decode(data, self.errors, final)
2019-11-01T10:55:19.197211820Z app[web.1]: UnicodeDecodeError: 'utf-8' codec can't decode