Got error running

[Gutem]

Follow install process on the README.en.md and got this error:
I'm on Ubuntu 20.04.1 LTS

$ python3 PackerFuzzer.py -u https://demo.poc-sir.com/

 ____            _               _____
|  _ \ __ _  ___| | _____ _ __  |  ___|   _ ___________ _ __
| |_) / _` |/ __| |/ / _ \ '__| | |_ | | | |_  /_  / _ \ '__|
|  __/ (_| | (__|   <  __/ |    |  _|| |_| |/ / / /  __/ |
|_|   \__,_|\___|_|\_\___|_|    |_|   \__,_/___/___\___|_|
                                Packer Fuzzer v1.2


©2021 Poc-Sir、KpLi0rn、Liucy、RachesseHS、Lupin-III
Project Hub: https://github.com/rtcatc/Packer-Fuzzer

[+] Network connectivity checked, current egress IP：152.254.225.102
[23:14:59] Target sites：https://demo.poc-sir.com/
[23:14:59] Parsing the page ...
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 159, in _new_conn
    conn = connection.create_connection(
  File "/usr/lib/python3/dist-packages/urllib3/util/connection.py", line 61, in create_connection
    for res in socket.getaddrinfo(host, port, family, socket.SOCK_STREAM):
  File "/usr/lib/python3.8/socket.py", line 918, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -2] Name or service not known

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 665, in urlopen
    httplib_response = self._make_request(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 376, in _make_request
    self._validate_conn(conn)
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 996, in _validate_conn
    conn.connect()
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 314, in connect
    conn = self._new_conn()
  File "/usr/lib/python3/dist-packages/urllib3/connection.py", line 171, in _new_conn
    raise NewConnectionError(
urllib3.exceptions.NewConnectionError: <urllib3.connection.VerifiedHTTPSConnection object at 0x7fc48fdcf910>: Failed to establish a new connection: [Errno -2] Name or service not known

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 439, in send
    resp = conn.urlopen(
  File "/usr/lib/python3/dist-packages/urllib3/connectionpool.py", line 719, in urlopen
    retries = retries.increment(
  File "/usr/lib/python3/dist-packages/urllib3/util/retry.py", line 436, in increment
    raise MaxRetryError(_pool, url, error or ResponseError(cause))
urllib3.exceptions.MaxRetryError: HTTPSConnectionPool(host='demo.poc-sir.com', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x7fc48fdcf910>: Failed to establish a new connection: [Errno -2] Name or service not known'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "PackerFuzzer.py", line 26, in <module>
    tt.check()
  File "PackerFuzzer.py", line 19, in check
    t.parseStart()
  File "/media/gutem/10TB/code/Packer-Fuzzer/lib/Controller.py", line 33, in parseStart
    ParseJs(projectTag, self.url, self.options).parseJsStart()
  File "/media/gutem/10TB/code/Packer-Fuzzer/lib/ParseJs.py", line 165, in parseJsStart
    self.requestUrl()
  File "/media/gutem/10TB/code/Packer-Fuzzer/lib/ParseJs.py", line 47, in requestUrl
    demo = requests.get(url=url, headers=headers,proxies=self.proxy_data).text
  File "/usr/lib/python3/dist-packages/requests/api.py", line 75, in get
    return request('get', url, params=params, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/api.py", line 60, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 533, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/lib/python3/dist-packages/requests/sessions.py", line 646, in send
    r = adapter.send(request, **kwargs)
  File "/usr/lib/python3/dist-packages/requests/adapters.py", line 516, in send
    raise ConnectionError(e, request=request)
requests.exceptions.ConnectionError: HTTPSConnectionPool(host='demo.poc-sir.com', port=443): Max retries exceeded with url: / (Caused by NewConnectionError('<urllib3.connection.VerifiedHTTPSConnection object at 0x7fc48fdcf910>: Failed to establish a new connection: [Errno -2] Name or service not known'))