Publishing or deleting a content view fails with error "duplicate key value violates unique constraint "cp_env_cnt_env_id_cntid_ky"" on Red Hat Satellite 6

Issue

• When publishing a new version of a composite content view, the process failed at 95 percent. The related task shows below error message:

  Runtime Error ERROR: duplicate key value violates unique constraint "cp_env_cnt_env_id_cntid_ky"
   Detail: Key (environment_id, contentid)=(2-21, 4185) already exists. at org.postgresql.core.v3.QueryExecutorImpl.receiveErrorResponse:2,157
  

• When deleting a content view, the delete operation fails with the above error.