Py3 adaptation

    Unrelated: RE-00

Change-Id: Id2f8f330003a7b53a7fbd11057113b0192376c74
diff --git a/requirements.txt b/requirements.txt
index eb04d44..2854391 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -5,3 +5,4 @@
 cmd2<0.9.0
 pbr>=1.6
 cliff>=1.4.5
+future