fetch_california_housing() URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749)>

Description

I am unable to use fetch_california_housing() to download sample data set. Looks like certificate may have expired?

Steps/Code to Reproduce

print(‘The scikit-learn version is {}.’.format(sklearn.version)) from sklearn.datasets import fetch_california_housing housing = fetch_california_housing()

Actual Results

Downloading Cal. housing from https://ndownloader.figshare.com/files/5976036 to /Users/test/scikit_learn_data
The scikit-learn version is 0.19.1.
---------------------------------------------------------------------------
SSLError                                  Traceback (most recent call last)
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in do_open(self, http_class, req, **http_conn_args)
   1317                 h.request(req.get_method(), req.selector, req.data, headers,
-> 1318                           encode_chunked=req.has_header('Transfer-encoding'))
   1319             except OSError as err: # timeout error

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py in request(self, method, url, body, headers, encode_chunked)
   1238         """Send a complete request to the server."""
-> 1239         self._send_request(method, url, body, headers, encode_chunked)
   1240 

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py in _send_request(self, method, url, body, headers, encode_chunked)
   1284             body = _encode(body, 'body')
-> 1285         self.endheaders(body, encode_chunked=encode_chunked)
   1286 

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py in endheaders(self, message_body, encode_chunked)
   1233             raise CannotSendHeader()
-> 1234         self._send_output(message_body, encode_chunked=encode_chunked)
   1235 

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py in _send_output(self, message_body, encode_chunked)
   1025         del self._buffer[:]
-> 1026         self.send(msg)
   1027 

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py in send(self, data)
    963             if self.auto_open:
--> 964                 self.connect()
    965             else:

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py in connect(self)
   1399             self.sock = self._context.wrap_socket(self.sock,
-> 1400                                                   server_hostname=server_hostname)
   1401             if not self._context.check_hostname and self._check_hostname:

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py in wrap_socket(self, sock, server_side, do_handshake_on_connect, suppress_ragged_eofs, server_hostname, session)
    400                          server_hostname=server_hostname,
--> 401                          _context=self, _session=session)
    402 

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py in __init__(self, sock, keyfile, certfile, server_side, cert_reqs, ssl_version, ca_certs, do_handshake_on_connect, family, type, proto, fileno, suppress_ragged_eofs, npn_protocols, ciphers, server_hostname, _context, _session)
    807                         raise ValueError("do_handshake_on_connect should not be specified for non-blocking sockets")
--> 808                     self.do_handshake()
    809 

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py in do_handshake(self, block)
   1060                 self.settimeout(None)
-> 1061             self._sslobj.do_handshake()
   1062         finally:

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py in do_handshake(self)
    682         """Start the SSL/TLS handshake."""
--> 683         self._sslobj.do_handshake()
    684         if self.context.check_hostname:

SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749)

During handling of the above exception, another exception occurred:

URLError                                  Traceback (most recent call last)
<ipython-input-18-dc07bc139b51> in <module>()
      1 print('The scikit-learn version is {}.'.format(sklearn.__version__))
      2 from sklearn.datasets import fetch_california_housing
----> 3 housing = fetch_california_housing()

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/sklearn/datasets/california_housing.py in fetch_california_housing(data_home, download_if_missing)
     99             ARCHIVE.url, data_home))
    100 
--> 101         archive_path = _fetch_remote(ARCHIVE, dirname=data_home)
    102 
    103         with tarfile.open(mode="r:gz", name=archive_path) as f:

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/sklearn/datasets/base.py in _fetch_remote(remote, dirname)
    872     file_path = (remote.filename if dirname is None
    873                  else join(dirname, remote.filename))
--> 874     urlretrieve(remote.url, file_path)
    875     checksum = _sha256(file_path)
    876     if remote.checksum != checksum:

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in urlretrieve(url, filename, reporthook, data)
    246     url_type, path = splittype(url)
    247 
--> 248     with contextlib.closing(urlopen(url, data)) as fp:
    249         headers = fp.info()
    250 

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in urlopen(url, data, timeout, cafile, capath, cadefault, context)
    221     else:
    222         opener = _opener
--> 223     return opener.open(url, data, timeout)
    224 
    225 def install_opener(opener):

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in open(self, fullurl, data, timeout)
    524             req = meth(req)
    525 
--> 526         response = self._open(req, data)
    527 
    528         # post-process response

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in _open(self, req, data)
    542         protocol = req.type
    543         result = self._call_chain(self.handle_open, protocol, protocol +
--> 544                                   '_open', req)
    545         if result:
    546             return result

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in _call_chain(self, chain, kind, meth_name, *args)
    502         for handler in handlers:
    503             func = getattr(handler, meth_name)
--> 504             result = func(*args)
    505             if result is not None:
    506                 return result

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in https_open(self, req)
   1359         def https_open(self, req):
   1360             return self.do_open(http.client.HTTPSConnection, req,
-> 1361                 context=self._context, check_hostname=self._check_hostname)
   1362 
   1363         https_request = AbstractHTTPHandler.do_request_

/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py in do_open(self, http_class, req, **http_conn_args)
   1318                           encode_chunked=req.has_header('Transfer-encoding'))
   1319             except OSError as err: # timeout error
-> 1320                 raise URLError(err)
   1321             r = h.getresponse()
   1322         except:

URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:749)>

[AEDWIP]

UGH!

I found the problem. python 3.6 on mac requires a post install step

$ less /Applications/Python\ 3.6/ReadMe.rtf

" Unlike previous releases, the deprecated Apple-supplied OpenSSL libraries are no longer used. This also means that the trust certificates in system and user keychains managed by the Keychain Access application and the security command line utility are no longer used as defaults"

The solution is

$ sudo /Applications/Python\ 3.6/Install\ Certificates.command

[nfrik]

Found solution here: http://blog.pengyifan.com/how-to-fix-python-ssl-certificate_verify_failed/

import os, ssl
if (not os.environ.get('PYTHONHTTPSVERIFY', '') and
    getattr(ssl, '_create_unverified_context', None)): 
    ssl._create_default_https_context = ssl._create_unverified_context