Red Hat Satellite 6 throws the exception: "ERF12-5356 [ProxyAPI::ProxyException]: Unable to get PuppetCA certificates"

Issue

• When navigating to Satellite WEBUI -> Infrastructure -> Capsules -> Action -> Certificates gets below error message:

 Operation FAILED: ERF12-5356 [ProxyAPI::ProxyException]: Unable to get PuppetCA certificates ([RestClient::NotAcceptable]: 406 Not Acceptable) for proxy https://satellite.example.com:9090/puppet/ca

• The following error is received in /var/log/foreman/production.log when doing a PXE boot and attempting an unattended provisioning of a system:

Found client.example.com
Remove puppet certificate for client.example.com
Operation FAILED: ERF12-7740 [ProxyAPI::ProxyException]: Unable to delete PuppetCA certificate for client.example.com ([RestClient::NotAcceptable]: 406 Not Acceptable) for proxy https://satellite.example.com:9090/puppet/ca
Completed 500 Internal Server Error in 161ms