Immutable user source: Non-admin V2 and V3 tests

If the keystone user source is immutable, such as an LDAP
active directory implementation, tempest tests that try
to create or delete a user will fail. Instead of failing,
we would like them to skip. This change uses a testtools
decorator to avoid unnecessary modifications and allow those tests
to skip. In [1], I introduced the config setting that allows
this to happen.

[1] https://review.openstack.org/#/c/585536/

Change-Id: I786499204acdb929ee341e014bcb0459d2f27483
Partial-Bug: 1777047

tempest/api/identity/v2/test_users.py

@@ -15,6 +15,8 @@
 
 import time
 
+import testtools
+
 from tempest.api.identity import base
 from tempest import config
 from tempest.lib.common.utils import data_utils
@@ -78,6 +80,10 @@ class IdentityUsersTest(base.BaseIdentityV2Test):
         self.non_admin_users_client.auth_provider.set_auth()
 
     @decorators.idempotent_id('165859c9-277f-4124-9479-a7d1627b0ca7')
+    @testtools.skipIf(CONF.identity_feature_enabled.immutable_user_source,
+                      'Skipped because environment has an '
+                      'immutable user source and solely '
+                      'provides read-only access to users.')
     def test_user_update_own_password(self):
         old_pass = self.creds.password
         old_token = self.non_admin_users_client.token

tempest/api/identity/v3/test_users.py

@@ -77,6 +77,10 @@ class IdentityV3UsersTest(base.BaseIdentityV3Test):
         self.non_admin_users_client.auth_provider.set_auth()
 
     @decorators.idempotent_id('ad71bd23-12ad-426b-bb8b-195d2b635f27')
+    @testtools.skipIf(CONF.identity_feature_enabled.immutable_user_source,
+                      'Skipped because environment has an '
+                      'immutable user source and solely '
+                      'provides read-only access to users.')
     def test_user_update_own_password(self):
         old_pass = self.creds.password
         old_token = self.non_admin_client.token
@@ -102,6 +106,10 @@ class IdentityV3UsersTest(base.BaseIdentityV3Test):
     @testtools.skipUnless(CONF.identity_feature_enabled.security_compliance,
                           'Security compliance not available.')
     @decorators.idempotent_id('941784ee-5342-4571-959b-b80dd2cea516')
+    @testtools.skipIf(CONF.identity_feature_enabled.immutable_user_source,
+                      'Skipped because environment has an '
+                      'immutable user source and solely '
+                      'provides read-only access to users.')
     def test_password_history_check_self_service_api(self):
         old_pass = self.creds.password
         new_pass1 = data_utils.rand_password()