add tox support to python unit tests

Change-Id: I7ed0e0fde335ec69395ee64fb0578ea59347de6b
diff --git a/packer/provision/basebuild.sh b/packer/provision/basebuild.sh
index e18dfee..596c24c 100644
--- a/packer/provision/basebuild.sh
+++ b/packer/provision/basebuild.sh
@@ -142,6 +142,7 @@
         robotframework-kafkalibrary \
         robotframework-requests \
         robotframework-sshlibrary \
+        tox \
         virtualenv
         # end of pip install list