Description of problem:

When I add a role to user on a specific tenant I get no indication if the operation succeeded or not . 
I prefer to get an object which represent the user details or alternately to get a message : "user role has been added successfully" or something similar . 

See additional information for more details . 

Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.
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Actual results:


Expected results:


Additional info:


[root@aqua-vds10 ~(keystone_admin)]# keystone user-list
+----------------------------------+---------+---------+-------------------+
|                id                |   name  | enabled |       email       |
+----------------------------------+---------+---------+-------------------+
| 5a5fee70ab7d4cab9bc93ca1bb65092c |  admin  |   True  |   test   |
| baeaba899b644f5db1ec68ccb4c14867 |  alice  |   True  | alice |
| 2770f42c57c74f678cb10e1c007bf78b |  cinder |   True  |  cinder@localhost |
| ea1c55f1e09141df81bd474dc0fb71db |  glance |   True  |  glance@localhost |
| 3885924867dd4a37978931fa293709ae |   nova  |   True  |   nova@localhost  |
| 7fb99e00501d42099b3dabfc20b3caec | quantum |   True  | quantum@localhost |
+----------------------------------+---------+---------+-------------------+
[root@aqua-vds10 ~(keystone_admin)]# keystone role-list
+----------------------------------+--------------+
|                id                |     name     |
+----------------------------------+--------------+
| 39ab475f8d364d7daa7e257bc97922f1 |    Member    |
| 9fe2ff9ee4384b1894a90878d3e92bab |   _member_   |
| 10a5365539434f96b7cb9a147739e294 |    admin     |
| 0c56d49148a6466f9aa6c349642f3316 | compute-user |
+----------------------------------+--------------+

[root@aqua-vds10 ~(keystone_admin)]# keystone tenant-list
+----------------------------------+----------+---------+
|                id                |   name   | enabled |
+----------------------------------+----------+---------+
| 50bed28de0cf4a94abb08b25bcee656a |   acme   |   True  |
| ebe2b14c28714976823150a0516b675b |  admin   |   True  |
| db2c4517468448349b9f96d4fc5c7d84 | services |   True  |
+----------------------------------+----------+---------+


## adding the user role first time 


[root@aqua-vds10 ~(keystone_admin)]# keystone user-role-add --user=baeaba899b644f5db1ec68ccb4c14867 --role=0c56d49148a6466f9aa6c349642f3316 --tenant-id=50bed28de0cf4a94abb08b25bcee656a
[root@aqua-vds10 ~(keystone_admin)]# 

## adding the user role second time


[root@aqua-vds10 ~(keystone_admin)]# keystone user-role-add --user=baeaba899b644f5db1ec68ccb4c14867 --role=0c56d49148a6466f9aa6c349642f3316 --tenant-id=50bed28de0cf4a94abb08b25bcee656a
Unable to communicate with identity service: {"error": {"message": "Conflict occurred attempting to store role grant. User baeaba899b644f5db1ec68ccb4c14867 already has role 0c56d49148a6466f9aa6c349642f3316 in tenant 50bed28de0cf4a94abb08b25bcee656a", "code": 409, "title": "Conflict"}}. (HTTP 409)