Bump xos libraries to version 4.0.0

Change-Id: If2cd9948426956a237e5ab65c3cfb724966bf521
diff --git a/Makefile b/Makefile
index b4a93fc..2554aad 100644
--- a/Makefile
+++ b/Makefile
@@ -60,7 +60,7 @@
 venv-service:
 	virtualenv $@;\
     source ./$@/bin/activate ; set -u ;\
-    pip install -r requirements.txt xosmigrate~=3.2.6
+    pip install -r requirements.txt xosmigrate~=4.0.0
 
 create-migration: venv-service
 	source ./venv-service/bin/activate; set -u;\