Ensure python is installed

devstack can call python before parsing the
package requirements, so the python installation
needs to be done eralier.

Closes-Bug: #1488625
Change-Id: I85cca899aeedd741cf7dc695435d61390e260f22
diff --git a/stack.sh b/stack.sh
index 825ed96..afb6958 100755
--- a/stack.sh
+++ b/stack.sh
@@ -335,6 +335,10 @@
     sudo sed -i "s/\(^127.0.0.1.*\)/\1 $LOCAL_HOSTNAME/" /etc/hosts
 fi
 
+# Ensure python is installed
+# --------------------------
+is_package_installed python || install_package python
+
 
 # Configure Logging
 # -----------------