Stop using oslotest.BaseTestCase

oslotest.BaseTestCase is going to be deprecated / removed in favor of using
the provided fixtures. oslotest.BaseTestCase does unnatural things with mock
cleanup that can't be fixed in a backwards-compatible way and we don't want
this odd cleanup or deprecation affecting our tests. See [1].

oslotest.BaseTestCase set up some fixtures that keystone didn't use:

 - timeout.Timeout
 - output.CaptureOutput
 - oslotest.log.ConfigureLogging

[1] https://review.openstack.org/#/c/280757/

Change-Id: I5d926fba83f0390fe06e75614d85d87d2cb9f285

.testr.conf

@@ -1,8 +1,5 @@
 [DEFAULT]
 test_command=
-    OS_STDOUT_CAPTURE=${OS_STDOUT_CAPTURE:-1} \
-    OS_STDERR_CAPTURE=${OS_STDERR_CAPTURE:-1} \
-    OS_LOG_CAPTURE=${OS_LOG_CAPTURE:-1} \
     ${PYTHON:-python} -m subunit.run discover -t ./ ${OS_TEST_PATH:-./keystone/tests/unit} $LISTOPT $IDOPTION
 
 test_id_option=--load-list $IDFILE

keystone/tests/unit/core.py

@@ -34,11 +34,11 @@ from oslo_config import fixture as config_fixture
 from oslo_log import fixture as log_fixture
 from oslo_log import log
 from oslo_utils import timeutils
-import oslotest.base as oslotest
 from oslotest import mockpatch
 from paste.deploy import loadwsgi
 import six
 from sqlalchemy import exc
+import testtools
 from testtools import testcase
 
 # NOTE(ayoung)
@@ -491,7 +491,7 @@ def create_user(api, domain_id, **kwargs):
     return user
 
 
-class BaseTestCase(oslotest.BaseTestCase):
+class BaseTestCase(testtools.TestCase):
     """Light weight base test class.
 
     This is a placeholder that will eventually go away once the
@@ -502,6 +502,10 @@ class BaseTestCase(oslotest.BaseTestCase):
 
     def setUp(self):
         super(BaseTestCase, self).setUp()
+
+        self.useFixture(fixtures.NestedTempfile())
+        self.useFixture(fixtures.TempHomeDir())
+
         self.useFixture(mockpatch.PatchObject(sys, 'exit',
                                               side_effect=UnexpectedExit))
         self.useFixture(log_fixture.get_logging_handle_error_fixture())