Upload on SSL - intermittent hang

When using `docs/publish.py` to publish to an IPFS server that is protected by SSL using Nginx as a reverse-proxy, I've noticed numerous instances of the script getting stuck waiting on

File "/usr/lib/python3.8/ssl.py", line 1099, in read
return self._sslobj.read(len, buffer)

It fails more often than it succeeds. It's not clear to me if this is an issue with the underlying SSL library (seems possible but unlikely), or Nginx (possible but also unlikely), or if there are some incorrect assumptions in the IPFS client about how it interacts with the IPFS server pushing numerous files up over a slow connection.

Example traceback, after pressing Ctrl+C to cancel it after its stuck:

> Traceback (most recent call last):
> File "publish.py", line 81, in
> sys.exit(main(sys.argv[1:]))
> File "publish.py", line 34, in main
> return publish(
> File "publish.py", line 55, in publish
> hash_docs = client.add("build/html", recursive=True, raw_leaves=True, pin=False)[-1]["Hash"]
> File "/home/c0llab0rat0r/code/github/self/py-ipfs-http-client/ipfshttpclient/client/files.py", line 373, in add
> resp = self._client.request('/add', decoder='json', data=body, headers=headers, **kwargs)
> File "/home/c0llab0rat0r/code/github/self/py-ipfs-http-client/ipfshttpclient/http_common.py", line 583, in request
> closables, res = self._request(
> File "/home/c0llab0rat0r/code/github/self/py-ipfs-http-client/ipfshttpclient/http_requests.py", line 165, in _request
> res = session.request(
> File "/home/c0llab0rat0r/code/github/self/py-ipfs-http-client/ipfshttpclient/requests_wrapper.py", line 230, in request
> return super().request(method, url, *args, **kwargs)
> File "/home/c0llab0rat0r/code/github/self/py-ipfs-http-client/venv/lib/python3.8/site-packages/requests/sessions.py", line 542, in request
> resp = self.send(prep, **send_kwargs)
> File "/home/c0llab0rat0r/code/github/self/py-ipfs-http-client/venv/lib/python3.8/site-packages/requests/sessions.py", line 655, in send
> r = adapter.send(request, **kwargs)
> File "/home/c0llab0rat0r/code/github/self/py-ipfs-http-client/venv/lib/python3.8/site-packages/requests/adapters.py", line 482, in send
> r = low_conn.getresponse()
> File "/usr/lib/python3.8/http/client.py", line 1347, in getresponse
> response.begin()
> File "/usr/lib/python3.8/http/client.py", line 307, in begin
> version, status, reason = self._read_status()
> File "/usr/lib/python3.8/http/client.py", line 268, in _read_status
> line = str(self.fp.readline(_MAXLINE + 1), "iso-8859-1")
> File "/usr/lib/python3.8/socket.py", line 669, in readinto
> return self._sock.recv_into(b)
> File "/usr/lib/python3.8/ssl.py", line 1241, in recv_into
> return self.read(nbytes, buffer)
> File "/usr/lib/python3.8/ssl.py", line 1099, in read
> return self._sslobj.read(len, buffer)