keystone charm makes wrong assumptions about charm directory, fails to deploy with juju-core

When deployed with juju-core, this error happens:
2013/04/25 13:53:14 INFO worker/uniter: HOOK Traceback (most recent call last):
2013/04/25 13:53:14 INFO worker/uniter: HOOK File "/var/lib/juju/agents/unit-keystone-0/charm/hooks/config-changed", line 535, in <module>
2013/04/25 13:53:14 INFO worker/uniter: HOOK utils.do_hooks(hooks)
2013/04/25 13:53:14 INFO worker/uniter: HOOK File "/var/lib/juju/agents/unit-keystone-0/charm/hooks/lib/utils.py", line 28, in do_hooks
2013/04/25 13:53:14 INFO worker/uniter: HOOK hook_func()
2013/04/25 13:53:14 INFO worker/uniter: HOOK File "/var/lib/juju/agents/unit-keystone-0/charm/hooks/config-changed", line 386, in config_changed
2013/04/25 13:53:14 INFO worker/uniter: HOOK save_script_rc(**env_vars)
2013/04/25 13:53:14 INFO worker/uniter: HOOK File "/var/lib/juju/agents/unit-keystone-0/charm/hooks/lib/openstack_common.py", line 226, in save_script_rc
2013/04/25 13:53:14 INFO worker/uniter: HOOK with open(juju_rc_path, 'wb') as rc_script:
2013/04/25 13:53:14 INFO worker/uniter: HOOK IOError: [Errno 2] No such file or directory: '/var/lib/juju/units/keystone-0/charm/scripts/scriptrc'

Note the charm directory layout changed between pyjuju and gojuju. In gojuju (juju-core) we have:
root@ip-10-191-189-143:/var/lib/juju# tree -d
.
├── agents
│   ├── machine-1
│   └── unit-keystone-0
│   ├── charm
│   │   ├── hooks
│   │   │   └── lib
│   │   ├── scripts
│   │   └── templates
│   └── state
│   ├── bundles
│   │   └── downloads
│   ├── deployer
│   │   ├── current -> /var/lib/juju/agents/unit-keystone-0/state/deployer/update-%Y%m%d-%H%M%S-0
│   │   └── update-%Y%m%d-%H%M%S-0
│   │   ├── hooks
│   │   │   └── lib
│   │   ├── scripts
│   │   └── templates
│   └── relations
└── tools
    ├── 1.10.0-precise-amd64
    ├── machine-1 -> 1.10.0-precise-amd64
    └── unit-keystone-0 -> 1.10.0-precise-amd64

(I hope the above renders correctly. If not: http://pastebin.ubuntu.com/5601103/)

It was suggested to use $CHARM_DIR instead, if the charm really needs to write that file somewhere inside the charm directory. It's exported by both pyjuju and gojuju.