Add venv package to the SL

Change-Id: I3999b6b41c6bccae0fe870a36ec3e5dd544b124a
diff --git a/tcp_tests/templates/shared-sl-tests.yaml b/tcp_tests/templates/shared-sl-tests.yaml
index 0cd49b3..00a9bb5 100644
--- a/tcp_tests/templates/shared-sl-tests.yaml
+++ b/tcp_tests/templates/shared-sl-tests.yaml
@@ -9,7 +9,7 @@
 - description: Install stacklight-pytest into virlual environemnt
   cmd: |
     set -e;
-    apt-get install -y  build-essential python-dev;
+    apt-get install -y  build-essential python-dev virtualenv;
     apt-get -y install python-virtualenv;
     virtualenv --system-site-packages venv-stacklight-pytest;
     . venv-stacklight-pytest/bin/activate;