I am running the following code in python3.6 to connect to a storage.
[root@controller wuwy]# python3
Python 3.6.8 (default, Jan 11 2019, 02:17:16)
[GCC 8.2.1 20180905 (Red Hat 8.2.1-3)] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pywbem
>>> ip = '193.168.11.113'
>>> user = '193_160_28_29'
>>> password = '193_160_28_29'
>>> url = 'https://193.168.11.113:5989'
>>> ca_certs = '/home/ca.cer'
>>> conn = pywbem.WBEMConnection(url,(user, password),default_namespace='root/example',ca_certs=ca_certs,no_verification=False)
>>> conn.EnumerateInstances('EXAMPLE_StorageProduct')

And I am getting the below error.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_operations.py", line 1919, in EnumerateInstances
    **extra)
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_operations.py", line 1232, in _imethodcall
    conn_id=self.conn_id)
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_http.py", line 776, in wbem_request
    client.endheaders()
  File "/usr/lib64/python3.6/http/client.py", line 1234, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/lib64/python3.6/http/client.py", line 1026, in _send_output
    self.send(msg)
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_http.py", line 461, in send
    self.connect()  # pylint: disable=no-member
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_http.py", line 619, in connect
    return self.sock.connect((self.host, self.port))
  File "/usr/lib64/python3.6/ssl.py", line 1064, in connect
    self._real_connect(addr, False)
  File "/usr/lib64/python3.6/ssl.py", line 1055, in _real_connect
    self.do_handshake()
  File "/usr/lib64/python3.6/ssl.py", line 1032, in do_handshake
    self._sslobj.do_handshake()
  File "/usr/lib64/python3.6/ssl.py", line 648, in do_handshake
    raise ValueError("check_hostname needs server_hostname "
ValueError: check_hostname needs server_hostname argument

When I am running the same code in python3.7, error changed.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/python3/lib/python3.7/site-packages/pywbem/_cim_operations.py", line 2494, in EnumerateInstances
    **extra)
  File "/usr/python3/lib/python3.7/site-packages/pywbem/_cim_operations.py", line 1763, in _imethodcall
    conn_id=self.conn_id)
  File "/usr/python3/lib/python3.7/site-packages/pywbem/_cim_http.py", line 824, in wbem_request
    client.endheaders()
  File "/usr/python3/lib/python3.7/http/client.py", line 1224, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/python3/lib/python3.7/http/client.py", line 1016, in _send_output
    self.send(msg)
  File "/usr/python3/lib/python3.7/site-packages/pywbem/_cim_http.py", line 483, in send
    self.connect()  # pylint: disable=no-member
  File "/usr/python3/lib/python3.7/site-packages/pywbem/_cim_http.py", line 661, in connect
    conn_id=conn_id)
pywbem._exceptions.ConnectionError: SSL error <class 'ssl.SSLCertVerificationError'>: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: IP address mismatch, certificate is not valid for '193.168.11.113'. (_ssl.c:1045); OpenSSL version: OpenSSL 1.1.1c FIPS  28 May 2019

This code works fine with python2.7 version.

And I checked the CN and SAN of the certificate, seems no problem here.

So could anyone tell me what's the problem here?

Are you running Python 2.7 on RHEL 7? Python 2.7 on RHEL 7 does not very certs by defaults, see https://access.redhat.com/articles/2039753

Could you please post the output of 'openssl x509 -text -in path/to/cert' for your certificate?

I am running Python on Centos7.
See result in attached file.

Your certificate does not have a subject alternative name extension. CN hostname matching has been deprecated for like 15 years. OpenSSL may ignore the CN and require a proper SAN extension of type IP general name.

You are right. I used openssl.cnf when created a csr, and ignore it when created cer.
Now the code works fine with python3.7, but still cannot work in python3.6.
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_operations.py", line 1919, in EnumerateInstances
    **extra)
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_operations.py", line 1232, in _imethodcall
    conn_id=self.conn_id)
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_http.py", line 776, in wbem_request
    client.endheaders()
  File "/usr/lib64/python3.6/http/client.py", line 1234, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/usr/lib64/python3.6/http/client.py", line 1026, in _send_output
    self.send(msg)
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_http.py", line 461, in send
    self.connect()  # pylint: disable=no-member
  File "/usr/local/lib/python3.6/site-packages/pywbem/cim_http.py", line 619, in connect
    return self.sock.connect((self.host, self.port))
  File "/usr/lib64/python3.6/ssl.py", line 1064, in connect
    self._real_connect(addr, False)
  File "/usr/lib64/python3.6/ssl.py", line 1055, in _real_connect
    self.do_handshake()
  File "/usr/lib64/python3.6/ssl.py", line 1032, in do_handshake
    self._sslobj.do_handshake()
  File "/usr/lib64/python3.6/ssl.py", line 648, in do_handshake
    raise ValueError("check_hostname needs server_hostname "
ValueError: check_hostname needs server_hostname argument

Could you please check the attached file for me again?

It's a different issue on 3.6. According to the exception message you are not passing server_hostname to wrap_socket().

I tried to print "self.host" which would be passed to wrap_socket().
It seems no problem.
> /usr/local/lib/python3.6/site-packages/pywbem/cim_http.py(616)connect()
-> try:
(Pdb) p self.host
'193.168.11.113'
(Pdb) n
> /usr/local/lib/python3.6/site-packages/pywbem/cim_http.py(617)connect()
-> self.sock = ctx.wrap_socket(sock,
(Pdb)
> /usr/local/lib/python3.6/site-packages/pywbem/cim_http.py(618)connect()
-> server_hostname=self.host)
(Pdb)
> /usr/local/lib/python3.6/site-packages/pywbem/cim_http.py(619)connect()
-> return self.sock.connect((self.host, self.port))
(Pdb)
ValueError: check_hostname needs server_hostname argument
> /usr/local/lib/python3.6/site-packages/pywbem/cim_http.py(619)connect()
-> return self.sock.connect((self.host, self.port))

I'm afraid I have to close this issue as OUT-OF-DATE. It's either a bug in pywbem or a 3.6-only bug. Python 3.6 is in security maintenance mode and no longer receive bug fixes.

I suggest that you take this issue to pywbem bug tracker and get assistance there.

OK. Thanks for your suggestion.