Add install_deps to ensure python dependencies are installed

Change-Id: I02d3954bfc607a4520e490913e4ad3001deec55b

hooks/install

@@ -17,4 +17,5 @@ for dep in ${DEPS[@]}; do
     check_and_install ${PYTHON} ${dep}
 done
 
+./hooks/install_deps
 exec ./hooks/install.real

hooks/install_deps

@@ -0,0 +1,18 @@
+#!/bin/bash
+# Wrapper to ensure that python dependencies are installed before we get into
+# the python part of the hook execution
+
+declare -a DEPS=('dnspython' 'pyudev')
+
+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

hooks/upgrade-charm

@@ -3,4 +3,5 @@
 # after we upgrade the charm with newer libraries
 rm -rf **/*.pyc
 
+./hooks/install_deps
 exec ./hooks/upgrade-charm.real