Imports oslo policy to fix test issues

Tests inheriting from keystone.tests.TestCase depend on having the
policy_file command-line option declared before setUp runs. Importing
the oslo policy module automatically declares the option.

Fixes-Bug: 1233224
Change-Id: I939bbdcb7df1c4a59108dced92d4d5c2e96defe2

keystone/tests/core.py

@@ -67,6 +67,11 @@
 from keystone.token import provider as token_provider
 from keystone import trust
 
+# NOTE(dstanek): Tests inheriting from TestCase depend on having the
+#   policy_file command-line option declared before setUp runs. Importing the
+#   oslo policy module automatically declares the option.
+from keystone.openstack.common import policy as common_policy  # noqa
+
 
 LOG = logging.getLogger(__name__)
 ROOTDIR = os.path.dirname(os.path.abspath('..'))