urllib3.exceptions.ProtocolError: ('Connection aborted.', OSError(0, 'Error'))

print("==============Compare to DJIA===========")
%matplotlib inline
# S&P 500: ^GSPC
# Dow Jones Index: ^DJI
# NASDAQ 100: ^NDX
backtest_plot(df_account_value,
baseline_ticker = '^DJI',
baseline_start = '2019-01-01',
baseline_end = '2021-01-01')

Exception in thread Thread-42:
Traceback (most recent call last):
File "/opt/conda/lib/python3.8/site-packages/urllib3/connectionpool.py", line 670, in urlopen
httplib_response = self._make_request(
File "/opt/conda/lib/python3.8/site-packages/urllib3/connectionpool.py", line 381, in _make_request
self._validate_conn(conn)
File "/opt/conda/lib/python3.8/site-packages/urllib3/connectionpool.py", line 978, in _validate_conn
conn.connect()
File "/opt/conda/lib/python3.8/site-packages/urllib3/connection.py", line 362, in connect
self.sock = ssl_wrap_socket(
File "/opt/conda/lib/python3.8/site-packages/urllib3/util/ssl_.py", line 386, in ssl_wrap_socket
return context.wrap_socket(sock, server_hostname=server_hostname)
File "/opt/conda/lib/python3.8/ssl.py", line 500, in wrap_socket
return self.sslsocket_class._create(
File "/opt/conda/lib/python3.8/ssl.py", line 1040, in _create
self.do_handshake()
File "/opt/conda/lib/python3.8/ssl.py", line 1309, in do_handshake
self._sslobj.do_handshake()
OSError: [Errno 0] Error

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/conda/lib/python3.8/site-packages/requests/adapters.py", line 439, in send
resp = conn.urlopen(
File "/opt/conda/lib/python3.8/site-packages/urllib3/connectionpool.py", line 726, in urlopen
retries = retries.increment(
File "/opt/conda/lib/python3.8/site-packages/urllib3/util/retry.py", line 410, in increment
raise six.reraise(type(error), error, _stacktrace)
File "/opt/conda/lib/python3.8/site-packages/urllib3/packages/six.py", line 734, in reraise
raise value.with_traceback(tb)
File "/opt/conda/lib/python3.8/site-packages/urllib3/connectionpool.py", line 670, in urlopen
httplib_response = self._make_request(
File "/opt/conda/lib/python3.8/site-packages/urllib3/connectionpool.py", line 381, in _make_request
self._validate_conn(conn)
File "/opt/conda/lib/python3.8/site-packages/urllib3/connectionpool.py", line 978, in _validate_conn
conn.connect()
File "/opt/conda/lib/python3.8/site-packages/urllib3/connection.py", line 362, in connect
self.sock = ssl_wrap_socket(
File "/opt/conda/lib/python3.8/site-packages/urllib3/util/ssl_.py", line 386, in ssl_wrap_socket
return context.wrap_socket(sock, server_hostname=server_hostname)
File "/opt/conda/lib/python3.8/ssl.py", line 500, in wrap_socket
return self.sslsocket_class._create(
File "/opt/conda/lib/python3.8/ssl.py", line 1040, in _create
self.do_handshake()
File "/opt/conda/lib/python3.8/ssl.py", line 1309, in do_handshake
self._sslobj.do_handshake()
urllib3.exceptions.ProtocolError: ('Connection aborted.', OSError(0, 'Error'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/opt/conda/lib/python3.8/threading.py", line 932, in _bootstrap_inner
self.run()
File "/opt/conda/lib/python3.8/threading.py", line 870, in run
self._target(*self._args, **self._kwargs)
File "/opt/conda/lib/python3.8/site-packages/multitasking/__init__.py", line 102, in _run_via_pool
return callee(*args, **kwargs)
File "/opt/conda/lib/python3.8/site-packages/yfinance/multi.py", line 167, in _download_one_threaded
data = _download_one(ticker, start, end, auto_adjust, back_adjust,
File "/opt/conda/lib/python3.8/site-packages/yfinance/multi.py", line 179, in _download_one
return Ticker(ticker).history(period=period, interval=interval,
File "/opt/conda/lib/python3.8/site-packages/yfinance/base.py", line 152, in history
data = self.session.get(url=url, params=params, proxies=proxy)
File "/opt/conda/lib/python3.8/site-packages/requests/api.py", line 76, in get
return request('get', url, params=params, **kwargs)
File "/opt/conda/lib/python3.8/site-packages/requests/api.py", line 61, in request
return session.request(method=method, url=url, **kwargs)
File "/opt/conda/lib/python3.8/site-packages/requests/sessions.py", line 530, in request
resp = self.send(prep, **send_kwargs)
File "/opt/conda/lib/python3.8/site-packages/requests/sessions.py", line 643, in send
r = adapter.send(request, **kwargs)
File "/opt/conda/lib/python3.8/site-packages/requests/adapters.py", line 498, in send
raise ConnectionError(err, request=request)
requests.exceptions.ConnectionError: ('Connection aborted.', OSError(0, 'Error'))