Drop django_openstack_auth related code

In Queens cycle, the code of django_openstack_auth was merged into
the horizon repository. The master branch of django_openstack_auth
will be retired. (horizon blueprint merge-openstack-auth)
This commit drops django_openstack_auth related code from DevStack.

_prepare_message_catalog_compilation in lib/horizon was used only
in install_django_openstack_auth, so it is dropped too.

Change-Id: If9467c520a1e07d1968b29e485df0097330356bc
diff --git a/tests/test_libs_from_pypi.sh b/tests/test_libs_from_pypi.sh
index 0bd8d49..a544b56 100755
--- a/tests/test_libs_from_pypi.sh
+++ b/tests/test_libs_from_pypi.sh
@@ -35,7 +35,7 @@
 ALL_LIBS+=" oslo.messaging oslo.log cliff stevedore"
 ALL_LIBS+=" python-cinderclient glance_store oslo.concurrency oslo.db"
 ALL_LIBS+=" oslo.versionedobjects oslo.vmware keystonemiddleware"
-ALL_LIBS+=" oslo.serialization django_openstack_auth"
+ALL_LIBS+=" oslo.serialization"
 ALL_LIBS+=" python-openstackclient osc-lib osc-placement"
 ALL_LIBS+=" os-client-config oslo.rootwrap"
 ALL_LIBS+=" oslo.i18n oslo.utils python-openstacksdk python-swiftclient"