subscription-manager commands fail with the error message: "Unable to verify server's identity: tlsv1 alert unknown ca"

Issue

• subscription-manager fails with the following error message:

  [root@example ~]# subscription-manager list --available 
  Unable to verify server's identity: tlsv1 alert unknown ca
  

• Errors are seen in /var/log/rhsm/rhsm.log:

  2015-03-27 19:16:20,927 [DEBUG] subscription-manager @connection.py:469 - Making request: PUT /rhsm/consumers/3415b3fe-c201-4433-abdc-d1518b3c607f
  2015-03-27 19:16:20,946 [ERROR] subscription-manager @cache.py:150 - Error updating system data on the server
  2015-03-27 19:16:20,946 [ERROR] subscription-manager @cache.py:151 - tlsv1 alert unknown ca
  

• When using third party SSL/CA certs, subscription-manager gives tlsv1 errors while registering:

  # subscription-manager register --org="xxxx" --activationkey="xxxxxxxxxx" --force
  The system has been registered with ID: 
  Unable to verify server's identity: tlsv1 alert unknown ca
  

• same error can appear when using yum:

  # yum check-update
  Loaded plugins: package_upload, product-id, search-disabled-repos,
  subscription-manager
  *tlsv1 alert unknown ca*