The Eclipse Tuleap plugin is requestiog the "user_groups" relative to a project and encounter the following problem :

Request URL
https://___________/api/projects/129/user_groups

Response Body

...
{
"id": "5",
"uri": "user_groups/5",
"label": "Utilisateurs enregistrés + restreints",
"users_uri": "user_groups/5/users",
"short_name": "authenticated_users",
"key": "ugroup_authenticated_users_name_key"
},
...

But :

Request URL

https://sds-0lyg.wks.era.sds.safran:443/api/user_groups/5/users?limit=10

Response Body

{
  "error": {
    "code": 404,
    "message": "Not Found: Unable to list the users of this group"
  }
}