tensorflow2, mnistが読み込めない

Question

前提・実現したいこと

tensorflow　の学習中にmnistのデータセットを用いようとしたのですが、以下のようなエラーが発生しました。なぜ発生するのかお教えいただきたいです。

発生している問題・エラーメッセージ

Downloading data from https://storage.googleapis.com/tensorflow/tf-keras-datasets/mnist.npz
---------------------------------------------------------------------------
SSLCertVerificationError                  Traceback (most recent call last)
/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in do_open(self, http_class, req, **http_conn_args)
   1318             try:
-> 1319                 h.request(req.get_method(), req.selector, req.data, headers,
   1320                           encode_chunked=req.has_header('Transfer-encoding'))

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py in request(self, method, url, body, headers, encode_chunked)
   1229         """Send a complete request to the server."""
-> 1230         self._send_request(method, url, body, headers, encode_chunked)
   1231 

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py in _send_request(self, method, url, body, headers, encode_chunked)
   1275             body = _encode(body, 'body')
-> 1276         self.endheaders(body, encode_chunked=encode_chunked)
   1277 

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py in endheaders(self, message_body, encode_chunked)
   1224             raise CannotSendHeader()
-> 1225         self._send_output(message_body, encode_chunked=encode_chunked)
   1226 

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py in _send_output(self, message_body, encode_chunked)
   1003         del self._buffer[:]
-> 1004         self.send(msg)
   1005 

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py in send(self, data)
    943             if self.auto_open:
--> 944                 self.connect()
    945             else:

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/http/client.py in connect(self)
   1398 
-> 1399             self.sock = self._context.wrap_socket(self.sock,
   1400                                                   server_hostname=server_hostname)

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ssl.py in wrap_socket(self, sock, server_side, do_handshake_on_connect, suppress_ragged_eofs, server_hostname, session)
    499         # ctx._wrap_socket()
--> 500         return self.sslsocket_class._create(
    501             sock=sock,

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ssl.py in _create(cls, sock, server_side, do_handshake_on_connect, suppress_ragged_eofs, server_hostname, context, session)
   1039                         raise ValueError("do_handshake_on_connect should not be specified for non-blocking sockets")
-> 1040                     self.do_handshake()
   1041             except (OSError, ValueError):

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/ssl.py in do_handshake(self, block)
   1308                 self.settimeout(None)
-> 1309             self._sslobj.do_handshake()
   1310         finally:

SSLCertVerificationError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1108)

During handling of the above exception, another exception occurred:

URLError                                  Traceback (most recent call last)
/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/tensorflow/python/keras/utils/data_utils.py in get_file(fname, origin, untar, md5_hash, file_hash, cache_subdir, hash_algorithm, extract, archive_format, cache_dir)
    262       try:
--> 263         urlretrieve(origin, fpath, dl_progress)
    264       except HTTPError as e:

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in urlretrieve(url, filename, reporthook, data)
    246 
--> 247     with contextlib.closing(urlopen(url, data)) as fp:
    248         headers = fp.info()

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in urlopen(url, data, timeout, cafile, capath, cadefault, context)
    221         opener = _opener
--> 222     return opener.open(url, data, timeout)
    223 

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in open(self, fullurl, data, timeout)
    524         sys.audit('urllib.Request', req.full_url, req.data, req.headers, req.get_method())
--> 525         response = self._open(req, data)
    526 

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in _open(self, req, data)
    541         protocol = req.type
--> 542         result = self._call_chain(self.handle_open, protocol, protocol +
    543                                   '_open', req)

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in _call_chain(self, chain, kind, meth_name, *args)
    501             func = getattr(handler, meth_name)
--> 502             result = func(*args)
    503             if result is not None:

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in https_open(self, req)
   1361         def https_open(self, req):
-> 1362             return self.do_open(http.client.HTTPSConnection, req,
   1363                 context=self._context, check_hostname=self._check_hostname)

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/urllib/request.py in do_open(self, http_class, req, **http_conn_args)
   1321             except OSError as err: # timeout error
-> 1322                 raise URLError(err)
   1323             r = h.getresponse()

URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1108)>

During handling of the above exception, another exception occurred:

Exception                                 Traceback (most recent call last)
<ipython-input-17-49e15817fb9c> in <module>
----> 1 m_data=mnist.load_data()

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/tensorflow/python/keras/datasets/mnist.py in load_data(path)
     56   """
     57   origin_folder = 'https://storage.googleapis.com/tensorflow/tf-keras-datasets/'
---> 58   path = get_file(
     59       path,
     60       origin=origin_folder + 'mnist.npz',

/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/tensorflow/python/keras/utils/data_utils.py in get_file(fname, origin, untar, md5_hash, file_hash, cache_subdir, hash_algorithm, extract, archive_format, cache_dir)
    265         raise Exception(error_msg.format(origin, e.code, e.msg))
    266       except URLError as e:
--> 267         raise Exception(error_msg.format(origin, e.errno, e.reason))
    268     except (Exception, KeyboardInterrupt) as e:
    269       if os.path.exists(fpath):

Exception: URL fetch failure on https://storage.googleapis.com/tensorflow/tf-keras-datasets/mnist.npz: None -- [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1108)

該当のソースコード

import tensorflow as tf
mnist = tf.keras.datasets.mnist
m_data=mnist.load_data()

試したこと

Exceptionで挙げられているurlに飛んでみると、no such objectと返されます。
しかし、書籍を見ても、他のサイトを見てもソースコードは同じなので困惑しています。

補足情報（FW/ツールのバージョンなど）

実行環境 Jupyter Notebook

Answer 1

具体的にどうすればよいか？を示す回答ではありませんが、参考まで。
mnistデータ取得
環境構築ガイド 〉 macOS環境のPython - SSL証明書のインストール

Comments

[Jumptt]

大変参考になる回答ありがとうございます。
過去質問に参照されていたリンクに飛び、
/Applications/Python\ 3.8/Install\ Certificates.command
/Applications/Python\ 3.8.2/Install\ Certificates.command
の両方をターミナルで実行したのですが、どちらもzsh: no such file or directoryとなってしまいました。

[8524ba23]

GUI上での操作を説明しているサイトが見つかりましたので回答に追記しています。

[Jumptt]

わざわざありがとうございます。
本当にたすかりました。