Remove deprecated test.idempotent_id decorator

All active tempest plugin now switched to use idempotent_id
from tempest.lib.decorators

Only usgae left is in 'networking-plumgrid' and x/valet tempest
plugin, both are blacklisted plugins.
- https://docs.openstack.org/tempest/latest/plugins/plugin-registry.html#blacklisted-plugins

networking-plumgrid fix is not merged since 3 years.
-I4872dbde4364692d49a98922cfb18beb784e77c3

We are safe to remove deprecated tempest.test.related_bug.

Change-Id: Iae3f3120de0fea9664e99fab59086f1a4994ae55
diff --git a/tempest/test.py b/tempest/test.py
index f383bc1..68602d6 100644
--- a/tempest/test.py
+++ b/tempest/test.py
@@ -38,12 +38,6 @@
 
 CONF = config.CONF
 
-# TODO(oomichi): This test.idempotent_id should be removed after all projects
-# switch to use decorators.idempotent_id.
-idempotent_id = debtcollector.moves.moved_function(
-    decorators.idempotent_id, 'idempotent_id', __name__,
-    version='Mitaka', removal_version='?')
-
 
 attr = debtcollector.moves.moved_function(
     decorators.attr, 'attr', __name__,
diff --git a/tempest/tests/test_decorators.py b/tempest/tests/test_decorators.py
index 6018441..1889420 100644
--- a/tempest/tests/test_decorators.py
+++ b/tempest/tests/test_decorators.py
@@ -19,7 +19,6 @@
 from tempest.common import utils
 from tempest import config
 from tempest import exceptions
-from tempest.lib.common.utils import data_utils
 from tempest import test
 from tempest.tests import base
 from tempest.tests import fake_config
@@ -33,47 +32,6 @@
                          fake_config.FakePrivate)
 
 
-# NOTE: The test module is for tempest.test.idempotent_id.
-# After all projects switch to use decorators.idempotent_id,
-# we can remove tempest.test.idempotent_id as well as this
-# test module
-class TestIdempotentIdDecorator(BaseDecoratorsTest):
-
-    def _test_helper(self, _id, **decorator_args):
-        @test.idempotent_id(_id)
-        def foo():
-            """Docstring"""
-            pass
-
-        return foo
-
-    def _test_helper_without_doc(self, _id, **decorator_args):
-        @test.idempotent_id(_id)
-        def foo():
-            pass
-
-        return foo
-
-    def test_positive(self):
-        _id = data_utils.rand_uuid()
-        foo = self._test_helper(_id)
-        self.assertIn('id-%s' % _id, getattr(foo, '__testtools_attrs'))
-        self.assertTrue(foo.__doc__.startswith('Test idempotent id: %s' % _id))
-
-    def test_positive_without_doc(self):
-        _id = data_utils.rand_uuid()
-        foo = self._test_helper_without_doc(_id)
-        self.assertTrue(foo.__doc__.startswith('Test idempotent id: %s' % _id))
-
-    def test_idempotent_id_not_str(self):
-        _id = 42
-        self.assertRaises(TypeError, self._test_helper, _id)
-
-    def test_idempotent_id_not_valid_uuid(self):
-        _id = '42'
-        self.assertRaises(ValueError, self._test_helper, _id)
-
-
 class TestServicesDecorator(BaseDecoratorsTest):
     def _test_services_helper(self, *decorator_args):
         class TestFoo(test.BaseTestCase):