Description of problem:

Unable to edit host_grp, host, puppet-classes upon creating an oscap policy

Processing by HostgroupsController#edit as HTML
  Parameters: {"id"=>"5-rhel66_grp"}
  Rendered puppetclasses/_selectedClasses.html.erb (4.5ms)
  Rendered puppetclasses/_classes_in_groups.html.erb (0.0ms)
  Rendered puppetclasses/_classes.html.erb (7.2ms)
  Rendered puppetclasses/_class_selection.html.erb (43.5ms)
  Rendered common/_domain.html.erb (218.5ms)
  Rendered common/_domain_subnet.html.erb (225.7ms)
  Rendered common/os_selection/_architecture.html.erb (4.5ms)
  Rendered common/os_selection/_operatingsystem.html.erb (26.0ms)
  Rendered common/os_selection/_initial.html.erb (34.0ms)
  Rendered puppetclasses/_class_parameters.html.erb (15.7ms)
  Rendered puppetclasses/_classes_parameters.html.erb (27.3ms)
  Rendered hostgroups/_form.html.erb (384.4ms)
  Rendered hostgroups/edit.html.erb within layouts/application (384.8ms)
Operation FAILED: only generation of JSON objects or arrays allowed
  Rendered common/500.html.erb within layouts/application (8.8ms)
  Rendered layouts/base.html.erb (1.5ms)
Completed 500 Internal Server Error in 454ms (Views: 15.1ms | ActiveRecord: 16.6ms)


Processing by PuppetclassesController#edit as HTML
  Parameters: {"id"=>"5-foreman_scap_client"}
  Rendered common/_edit_habtm.html.erb (7.1ms)
  Rendered lookup_keys/_value.html.erb (215.0ms)
  Rendered lookup_keys/_fields.html.erb (254.4ms)
  Rendered lookup_keys/_value.html.erb (9.1ms)
  Rendered lookup_keys/_fields.html.erb (66.0ms)
Client connected.
Connected to server.
  Rendered lookup_keys/_value.html.erb (6.2ms)
  Rendered lookup_keys/_fields.html.erb (251.6ms)
  Rendered lookup_keys/_fields.html.erb (21.3ms)
  Rendered puppetclasses/_form.html.erb (649.1ms)
  Rendered puppetclasses/edit.html.erb within layouts/application (649.6ms)
Operation FAILED: only generation of JSON objects or arrays allowed
  Rendered common/500.html.erb within layouts/application (6.6ms)
  Rendered layouts/base.html.erb (1.3ms)
Completed 500 Internal Server Error in 684ms (Views: 10.4ms | ActiveRecord: 9.1ms)


Version-Release number of selected component (if applicable):
sat6.1 beta snap3

How reproducible:
upon creating an oscap policy

Steps to Reproduce:
1. create puppet_Repo, sync, puppet_cv , publish promote
2. make sure puppet-classes is visible
3. create a hostgroup, till this stage we would be able to edit the entities created in step 2) and 3).
4. Now create an oscap policy, after the policy is created the existing hostgroups and puppet-classes can no longer be edited.

Actual results:
unable to edit host-groups, foreman_scap_client or hosts 

We get the below message:
Operation FAILED: only generation of JSON objects or arrays allowed.

It appears that all entities for which foreman_scap_client puppet-class is associated cannot be edited.

Expected results:
editing of hostgroup and puppet-classes should be possible even after oscap policy creation.

Additional info: