Using a newer xosmigrate library

Change-Id: I1562517fc9599f1a8fa4df948c2d291bbd65a43d
diff --git a/Makefile b/Makefile
index 104f117..e3dc85d 100644
--- a/Makefile
+++ b/Makefile
@@ -60,7 +60,7 @@
 venv-service:
 	virtualenv $@;\
     source ./$@/bin/activate ; set -u ;\
-    pip install -r requirements.txt xosmigrate~=3.2.1
+    pip install -r requirements.txt xosmigrate~=3.2.6
 
 create-migration: venv-service
 	source ./venv-service/bin/activate; set -u;\