Why attempting unattended provisioning fails with error on Red Hat Satellite 6?

Issue

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

  Processing by UnattendedController#provision as */*
   Parameters: {"token"=>"e644ea0a-8824-4483-86fa-dde3a967e030"}
  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
  
  ArgumentError (There was no default layout for UnattendedController in #<ActionView::PathSet:0x0000001015a850 @paths=[/usr/share/foreman/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/katello-1.5.0/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/katello-1.5.0/engines/bastion/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/ui_alchemy-rails-1.0.12/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/foreman-tasks-0.6.9/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/foreman_bootdisk-2.0.6/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/redhat_access-0.0.4/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/foreman_discovery-1.3.0/app/views, /opt/rh/ruby193/root/usr/share/gems/gems/apipie-rails-0.2.5/app/views]>):
   app/controllers/application_controller.rb:313:in `generic_exception'
   lib/middleware/catch_json_parse_errors.rb:9:in `call'
   lib/proxy_api/puppetca.rb:41:in `rescue in del_certificate'
   lib/proxy_api/puppetca.rb:36:in `del_certificate'
   app/models/concerns/orchestration/puppetca.rb:23:in `delCertificate'
   app/models/host/managed.rb:256:in `handle_ca'
   app/controllers/unattended_controller.rb:161:in `handle_ca'
   app/models/concerns/foreman/thread_session.rb:33:in `clear_thread'
  

• When trying to kickstart a system, I see the curl request traing to fetch the kickstart file and printing 500 Internal Server Error