test_imaplib fail when installing python3.6.1 on centos6.9

[Wade Wang]

Hello, everyone. I'm trying to install Python 3.6.1 on my CentOS 6.9
server, but test_imaplib always fails its test when make test. Here is what
I got:

> ======================================================================
> ERROR: test_logincapa_with_client_certfile (test.test_imaplib.RemoteIMAP_
SSLTest)
> ----------------------------------------------------------------------
> Traceback (most recent call last):
>   File "/root/Python-3.6.1/Lib/test/test_imaplib.py", line 973, in
test_logincapa_with_client_certfile
>     certfile=CERTFILE)
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 1280, in __init__
>     IMAP4.__init__(self, host, port)
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 197, in __init__
>     self.open(host, port)
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 1293, in open
>     IMAP4.open(self, host, port)
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 294, in open
>     self.sock = self._create_socket()
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 1285, in _create_socket
>     server_hostname=self.host)
>   File "/root/Python-3.6.1/Lib/ssl.py", line 401, in wrap_socket
>     _context=self, _session=session)
>   File "/root/Python-3.6.1/Lib/ssl.py", line 808, in __init__
>     self.do_handshake()
>   File "/root/Python-3.6.1/Lib/ssl.py", line 1061, in do_handshake
>     self._sslobj.do_handshake()
>   File "/root/Python-3.6.1/Lib/ssl.py", line 683, in do_handshake
>     self._sslobj.do_handshake()
> ssl.SSLError: [SSL: TLSV1_ALERT_UNKNOWN_CA] tlsv1 alert unknown ca
(_ssl.c:749)
>
> ======================================================================
> ERROR: test_logincapa_with_client_ssl_context
(test.test_imaplib.RemoteIMAP_SSLTest)
> ----------------------------------------------------------------------
> Traceback (most recent call last):
>   File "/root/Python-3.6.1/Lib/test/test_imaplib.py", line 979, in
> test_logincapa_with_client_ssl_context
>     self.host, self.port, ssl_context=self.create_ssl_context())
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 1280, in __init__
>     IMAP4.__init__(self, host, port)
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 197, in __init__
>     self.open(host, port)
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 1293, in open
>     IMAP4.open(self, host, port)
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 294, in open
>     self.sock = self._create_socket()
>   File "/root/Python-3.6.1/Lib/imaplib.py", line 1285, in _create_socket
>     server_hostname=self.host)
>   File "/root/Python-3.6.1/Lib/ssl.py", line 401, in wrap_socket
>     _context=self, _session=session)
>   File "/root/Python-3.6.1/Lib/ssl.py", line 808, in __init__
>     self.do_handshake()
>   File "/root/Python-3.6.1/Lib/ssl.py", line 1061, in do_handshake
>     self._sslobj.do_handshake()
>   File "/root/Python-3.6.1/Lib/ssl.py", line 683, in do_handshake
>     self._sslobj.do_handshake()
> ssl.SSLError: [SSL: TLSV1_ALERT_UNKNOWN_CA] tlsv1 alert unknown ca
(_ssl.c:749)
>
> ----------------------------------------------------------------------
> Ran 95 tests in 27.005s
>
> FAILED (errors=2)
> 1 test failed again:
>     test_imaplib
>
> Total duration: 6 min 34 sec
> Tests result: FAILURE
> make: *** [test] Error 1

Any solution or suggestion?