[Satellite6] foreman-proxy error 406 Cannot find puppet_ssl_ca file

Issue

Various actions like:

• a new content view publish
• import puppet classes
• work with puppet environments

fail with foreman-proxy 406 error: Cannot find puppet_ssl_ca file /var/lib/puppet/ssl/certs/ca.pem.

The file /var/lib/puppet/ssl/certs/ca.pem exists and have proper file permissions and ownership, though.