Install oslo.i18n from source

Add a step to install oslo.i18n from source.

Change-Id: Ie041d4b82ca75a1c2ff99563a7a87447adc57ad2
diff --git a/stackrc b/stackrc
index 3923d38..8aa478f 100644
--- a/stackrc
+++ b/stackrc
@@ -183,6 +183,10 @@
 OSLODB_REPO=${OSLODB_REPO:-${GIT_BASE}/openstack/oslo.db.git}
 OSLODB_BRANCH=${OSLODB_BRANCH:-master}
 
+# oslo.i18n
+OSLOI18N_REPO=${OSLOI18N_REPO:-${GIT_BASE}/openstack/oslo.i18n.git}
+OSLOI18N_BRANCH=${OSLOI18N_BRANCH:-master}
+
 # oslo.messaging
 OSLOMSG_REPO=${OSLOMSG_REPO:-${GIT_BASE}/openstack/oslo.messaging.git}
 OSLOMSG_BRANCH=${OSLOMSG_BRANCH:-master}