请帮助我，我在尝试使用TensorFlow下载MNIST数据集时遇到了以下错误。

Using TensorFlow backend.Downloading data from https://s3.amazonaws.com/img-datasets/mnist.npzTraceback (most recent call last):  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 1318, in do_open    encode_chunked=req.has_header('Transfer-encoding'))  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1239, in request    self._send_request(method, url, body, headers, encode_chunked)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1285, in _send_request    self.endheaders(body, encode_chunked=encode_chunked)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1234, in endheaders    self._send_output(message_body, encode_chunked=encode_chunked)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1026, in _send_output    self.send(msg)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 964, in send    self.connect()  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1400, in connect    server_hostname=server_hostname)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 401, in wrap_socket    _context=self, _session=session)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 808, in __init__    self.do_handshake()  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 1061, in do_handshake    self._sslobj.do_handshake()  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 683, in do_handshake    self._sslobj.do_handshake()ssl.SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749)

在处理上述异常时，发生了另一个异常：

Traceback (most recent call last):  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/keras/utils/data_utils.py", line 207, in get_file    urlretrieve(origin, fpath, dl_progress)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 248, in urlretrieve    with contextlib.closing(urlopen(url, data)) as fp:  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 223, in urlopen    return opener.open(url, data, timeout)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 526, in open    response = self._open(req, data)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 544, in _open    '_open', req)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 504, in _call_chain    result = func(*args)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 1361, in https_open    context=self._context, check_hostname=self._check_hostname)  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 1320, in do_open    raise URLError(err)urllib.error.URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749)>

在处理上述异常时，发生了另一个异常：

Traceback (most recent call last):  File "/Users/lorin/Applications/miniconda3/envs/udemy/mnist_keras.py", line 13, in <module>    (X_train, y_train), (X_test, y_test) = mnist.load_data('/lib/python3.6/site-packages/keras/datasetsmnist.py')  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/keras/datasets/mnist.py", line 15, in load_data    path = get_file(path, origin='https://s3.amazonaws.com/img-datasets/mnist.npz')  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/keras/utils/data_utils.py", line 209, in get_file    raise Exception(error_msg.format(origin, e.errno, e.reason))Exception: URL fetch failure on https://s3.amazonaws.com/img-datasets/mnist.npz: None -- [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749)

进程以退出代码 enter code here 结束

回答：

我建议您在单独的虚拟环境中安装TensorFlow。

请按照以下步骤操作：在虚拟环境中安装TensorFlow

请始终记得在每次使用TensorFlow的新shell中激活virtualenv环境，运行以下命令：
$ source ~/<target_directory>/bin/activate