Red Hat Satellite 5.6 gives Internal Server Error, with "Could not parse acl statement 'valid-user'" error in httpd logs

Issue

• Red Hat Satellite 5.6 gives Internal Server Error when working with server groups or other Perl (pxt) pages:

# cat /var/log/httpd/ssl_error.log
[...]
[Mon Mar 10 13:35:56 2014] [error] [client 10.13.140.1] Could not parse acl statement 'valid-user';
 at /usr/share/perl5/vendor_perl/PXT/ACL.pm line 90.\n, referer: https://satellite.example.com/network/systems/groups/details.pxt?sgid=16