Ensure python2 is installed before hook execution

hooks/glance_relations.py

@@ -95,7 +95,7 @@ hooks = Hooks()
 CONFIGS = register_configs()
 
 
-@hooks.hook('install')
+@hooks.hook('install.real')
 def install_hook():
     juju_log('Installing glance packages')
     execd_preinstall()

hooks/install

@@ -1 +0,0 @@
-glance_relations.py

hooks/install

@@ -0,0 +1,20 @@
+#!/bin/bash
+# Wrapper to deal with newer Ubuntu versions that don't have py2 installed
+# by default.
+
+declare -a DEPS=('apt' 'netaddr' 'netifaces' 'pip' 'yaml')
+
+check_and_install() {
+    pkg="${1}-${2}"
+    if ! dpkg -s ${pkg} 2>&1 > /dev/null; then
+        apt-get -y install ${pkg}
+    fi
+}
+
+PYTHON="python"
+
+for dep in ${DEPS[@]}; do
+    check_and_install ${PYTHON} ${dep}
+done
+
+exec ./hooks/install.real

hooks/install.real

@@ -0,0 +1 @@
+glance_relations.py