Why does yum throw errors like M2Crypto.SSL.SSLError certificate verify failed when executed?

Issue

• System is registered with RHN classic. When yum commands are executed, it throws the following errors.

  #yum repolist
  Loaded plugins: product-id, rhnplugin, security, subscription-manager
  certificate verify failed
  This system is not registered with RHN Classic or RHN Satellite.
  You can use rhn_register to register.
  RHN Satellite or RHN Classic support will be disabled.
  dvd-server                                                                     | 1.5 kB     00:00
  dvd-server/primary                                                             | 945 kB     00:00
  dvd-server                                                                              3363/3363
  Traceback (most recent call last):
    File "/usr/bin/yum", line 29, in ?
      yummain.user_main(sys.argv[1:], exit_code=True)
    File "/usr/share/yum-cli/yummain.py", line 309, in user_main
      errcode = main(args)
    File "/usr/share/yum-cli/yummain.py", line 178, in main
      result, resultmsgs = base.doCommands()
    File "/usr/share/yum-cli/cli.py", line 349, in doCommands
      return self.yum_cli_commands[self.basecmd].doCommand(self, self.basecmd, self.extcmds)
    File "/usr/share/yum-cli/yumcommands.py", line 788, in doCommand
      base.repos.populateSack()
    File "/usr/lib/python2.4/site-packages/yum/repos.py", line 260, in populateSack
      sack.populate(repo, mdtype, callback, cacheonly)
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 168, in populate
      if self._check_db_version(repo, mydbtype):
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 226, in _check_db_version
      return repo._check_db_version(mdtype)
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1226, in _check_db_version
      repoXML = self.repoXML
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1399, in <lambda>
      repoXML = property(fget=lambda self: self._getRepoXML(),
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1391, in _getRepoXML
      self._loadRepoXML(text=self)
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1381, in _loadRepoXML
      return self._groupLoadRepoXML(text, ["primary"])
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1365, in _groupLoadRepoXML
      if self._commonLoadRepoXML(text):
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 1201, in _commonLoadRepoXML
      result = self._getFileRepoXML(local, text)
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 974, in _getFileRepoXML
      cache=self.http_caching == 'all')
    File "/usr/lib/python2.4/site-packages/yum/yumRepo.py", line 811, in _getFile
      http_headers=headers,
    File "/usr/lib/python2.4/site-packages/urlgrabber/mirror.py", line 412, in urlgrab
      return self._mirror_try(func, url, kw)
    File "/usr/lib/python2.4/site-packages/urlgrabber/mirror.py", line 398, in _mirror_try
      return func_ref( *(fullurl,), **kwargs )
    File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 936, in urlgrab
      return self._retry(opts, retryfunc, url, filename)
    File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 854, in _retry
      r = apply(func, (opts,) + args, {})
    File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 922, in retryfunc
      fo = URLGrabberFileObject(url, filename, opts)
    File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 1010, in __init__
      self._do_open()
    File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 1093, in _do_open
      fo, hdr = self._make_request(req, opener)
    File "/usr/lib/python2.4/site-packages/urlgrabber/grabber.py", line 1202, in _make_request
      fo = opener.open(req)
    File "/usr/lib64/python2.4/urllib2.py", line 358, in open
      response = self._open(req, data)
    File "/usr/lib64/python2.4/urllib2.py", line 376, in _open
      '_open', req)
    File "/usr/lib64/python2.4/urllib2.py", line 337, in _call_chain
      result = func(*args)
    File "/usr/lib64/python2.4/site-packages/M2Crypto/m2urllib2.py", line 82, in https_open
      h.request(req.get_method(), req.get_selector(), req.data, headers)
    File "/usr/lib64/python2.4/httplib.py", line 810, in request
      self._send_request(method, url, body, headers)
    File "/usr/lib64/python2.4/httplib.py", line 833, in _send_request
      self.endheaders()
    File "/usr/lib64/python2.4/httplib.py", line 804, in endheaders
      self._send_output()
    File "/usr/lib64/python2.4/httplib.py", line 685, in _send_output
      self.send(msg)
    File "/usr/lib64/python2.4/httplib.py", line 652, in send
      self.connect()
    File "/usr/lib64/python2.4/site-packages/M2Crypto/httpslib.py", line 55, in connect
      sock.connect((self.host, self.port))
    File "/usr/lib64/python2.4/site-packages/M2Crypto/SSL/Connection.py", line 174, in connect
      ret = self.connect_ssl()
    File "/usr/lib64/python2.4/site-packages/M2Crypto/SSL/Connection.py", line 167, in connect_ssl
      return m2.ssl_connect(self.ssl, self._timeout)
  M2Crypto.SSL.SSLError: certificate verify failed