Fix invocation python2 -> python3

Change-Id: Ic78da9c03e99f59d142c93394051bbc2751f0205
diff --git a/contrib/jenkins.sh b/contrib/jenkins.sh
index a70f139..5ba2c8d 100755
--- a/contrib/jenkins.sh
+++ b/contrib/jenkins.sh
@@ -9,7 +9,7 @@
 	exit 1
 fi
 
-virtualenv -p python2 venv --system-site-packages
+virtualenv -p python3 venv --system-site-packages
 . venv/bin/activate
 pip install pytlv
 pip install pyyaml