Add test=True suport in keystonev3.py

PROD-34615

Change-Id: I9f2e2b47c7cc74eb0d243a2aae738f1989c373ca
diff --git a/tests/test-requirements.txt b/tests/test-requirements.txt
index 7188b2b..bc7dc7f 100644
--- a/tests/test-requirements.txt
+++ b/tests/test-requirements.txt
@@ -1,3 +1,4 @@
 jsonschema
 reno
 setuptools<45.0.0
+msgpack<1.0.0