ReadTimeout

There is an error while retrieving list of files from folder with almost 100k files. But all files were retrieved successfully.
```
Traceback (most recent call last):
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/connectionpool.py", line 386, in _make_request
six.raise_from(e, None)
File "", line 2, in raise_from
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/connectionpool.py", line 382, in _make_request
httplib_response = conn.getresponse()
File ".pyenv/versions/3.6.4/lib/python3.6/http/client.py", line 1331, in getresponse
response.begin()
File ".pyenv/versions/3.6.4/lib/python3.6/http/client.py", line 297, in begin
version, status, reason = self._read_status()
File ".pyenv/versions/3.6.4/lib/python3.6/http/client.py", line 258, in _read_status
line = str(self.fp.readline(_MAXLINE + 1), "iso-8859-1")
File ".pyenv/versions/3.6.4/lib/python3.6/socket.py", line 586, in readinto
return self._sock.recv_into(b)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/contrib/pyopenssl.py", line 291, in recv_into
raise timeout('The read operation timed out')
socket.timeout: The read operation timed out

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/requests/adapters.py", line 445, in send
timeout=timeout
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/connectionpool.py", line 649, in urlopen
_stacktrace=sys.exc_info()[2])
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/util/retry.py", line 357, in increment
raise six.reraise(type(error), error, _stacktrace)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/packages/six.py", line 686, in reraise
raise value
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/connectionpool.py", line 600, in urlopen
chunked=chunked)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/connectionpool.py", line 388, in _make_request
self._raise_timeout(err=e, url=url, timeout_value=read_timeout)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/urllib3/connectionpool.py", line 308, in _raise_timeout
raise ReadTimeoutError(self, url, "Read timed out. (read timeout=%s)" % timeout_value)
urllib3.exceptions.ReadTimeoutError: HTTPSConnectionPool(host='api.dropboxapi.com', port=443): Read timed out. (read timeout=30)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "apps/creatives_manager/processors/base.py", line 144, in _get_files_from_dropbox
result = self.dropbox.files_list_folder_continue(result.cursor)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/dropbox/base.py", line 1583, in files_list_folder_continue
None,
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/dropbox/dropbox.py", line 274, in request
timeout=timeout)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/dropbox/dropbox.py", line 365, in request_json_string_with_retry
timeout=timeout)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/dropbox/dropbox.py", line 449, in request_json_string
timeout=timeout,
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/requests/sessions.py", line 559, in post
return self.request('POST', url, data=data, json=json, **kwargs)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/requests/sessions.py", line 512, in request
resp = self.send(prep, **send_kwargs)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/requests/sessions.py", line 622, in send
r = adapter.send(request, **kwargs)
File ".pyenv/versions/marketing-ua-reports/lib/python3.6/site-packages/requests/adapters.py", line 526, in send
raise ReadTimeout(e, request=request)
requests.exceptions.ReadTimeout: HTTPSConnectionPool(host='api.dropboxapi.com', port=443): Read timed out. (read timeout=30)
```

Repeating of call `self.dropbox.files_list_folder_continue(result.cursor)` and enlarging timeout don't help.