GET `role/{id}` doesn't give error if id doesn't exist
The following is not consistent in the API:

GET organization/999 -> `"msg": "Organization id=999 not found!"` (status 404)
GET user/999 -> `"msg": "user id=999 is not found"`  (status 404)
(same for other resources)

however, for `role` we find:

GET role/999 -> `{}` (empty dictionary, status 200)

We need to adjust the role endpoint to also yield an error instead of an empty dictionary
diff --git a/vantage6-server/vantage6/server/resource/role.py b/vantage6-server/vantage6/server/resource/role.py
index 3971cf8b..5a052868 100644
--- a/vantage6-server/vantage6/server/resource/role.py
+++ b/vantage6-server/vantage6/server/resource/role.py
@@ -296,6 +296,10 @@ class Role(RoleBase):
     def get(self, id):
         role = db.Role.get(id)
 
+        if not role:
+            return {"msg": f"Role with id={id} not found."}, \\
+                HTTPStatus.NOT_FOUND
+
         # check permissions. A user can always view their own roles
         if not (self.r.v_glo.can() or role in g.user.roles):
             if not (self.r.v_org.can()
['vantage6-server/vantage6/server/resource/role.py']