haproxy missing install dependency

Hi,

I used the haproxy charm on digitalocean and noticed that it's missing a dependency on python-yaml. That package is probably installed in the ubuntu cloud images elsewhere, but not in DO's:
2014-04-04 14:20:19 INFO juju.worker.uniter uniter.go:469 running "install" hook
2014-04-04 14:20:19 INFO worker.uniter.jujuc server.go:103 running hook tool "juju-log" ["Invoking charm-pre-install hooks"]
2014-04-04 14:20:19 DEBUG worker.uniter.jujuc server.go:104 hook context id "haproxy/0:install:1366138670011990355"; dir "/var/lib/juju/agents/unit-haproxy-0/charm"
2014-04-04 14:20:19 INFO juju-log Invoking charm-pre-install hooks
2014-04-04 14:20:19 INFO worker.uniter.jujuc server.go:103 running hook tool "juju-log" ["Invoking python-based install hook"]
2014-04-04 14:20:19 DEBUG worker.uniter.jujuc server.go:104 hook context id "haproxy/0:install:1366138670011990355"; dir "/var/lib/juju/agents/unit-haproxy-0/charm"
2014-04-04 14:20:19 INFO juju-log Invoking python-based install hook
2014-04-04 14:20:19 INFO install Traceback (most recent call last):
2014-04-04 14:20:19 INFO install File "hooks/hooks.py", line 11, in <module>
2014-04-04 14:20:19 INFO install import yaml
2014-04-04 14:20:19 INFO install ImportError: No module named yaml
2014-04-04 14:20:19 ERROR juju.worker.uniter uniter.go:475 hook failed: exit status 1

Suggested fix:
--- install.orig 2014-04-04 10:38:05.260191000 -0400
+++ install 2014-04-04 10:38:19.972191000 -0400
@@ -6,6 +6,8 @@
     DEBIAN_FRONTEND=noninteractive apt-get -y -qq -o Dpkg::Options::="--force-confdef" -o Dpkg::Options::="--force-confold" install $@
 }

+apt_get_install python-yaml
+
 juju-log 'Invoking charm-pre-install hooks'
 [ -d exec.d ] && ( for f in exec.d/*/charm-pre-install; do [ -x $f ] && /bin/sh -c "$f"; done )