Add a test for modifying a role to set the name the same

There was no test that showed what happened when a role is modified
to have the same name. The test shows that when using the LDAP
assignment this request fails with a conflict error.

(cherry picked from commit 79c2fedd6f)

Change-Id: I40bb62200e79c8ff519e02facad042a657c26cae
Partial-Bug: #1401721

keystone/tests/test_backend.py

@@ -3328,6 +3328,13 @@ class IdentityTests(object):
                                         {'description': uuid.uuid4().hex})
         # If the previous line didn't raise an exception then the test passes.
 
+    def test_update_role_same_name(self):
+        # A user can update a role and set the name to be the same as it was.
+
+        self.assignment_api.update_role(self.role_member['id'],
+                                        {'name': self.role_member['name']})
+        # If the previous line didn't raise an exception then the test passes.
+
 
 class TokenTests(object):
     def _create_token_id(self):

keystone/tests/test_backend_ldap.py

@@ -1825,6 +1825,14 @@ class LDAPIdentity(BaseLDAPIdentity, tests.TestCase):
         self.assertEqual('crap', user_ref['id'])
         self.assertEqual('Foo Bar', user_ref['name'])
 
+    def test_update_role_same_name(self):
+        # Override
+        # This test is failing using the LDAP assignment backend, see
+        # bug 1401721.
+        # FIXME(blk-u): This should work.
+        self.assertRaises(exception.Conflict,
+                          super(LDAPIdentity, self).test_update_role_same_name)
+
 
 class LDAPIdentityEnabledEmulation(LDAPIdentity):
     def setUp(self):