I am trying to run the Charm tutorial from the juju documentation by creating a new charm from a local repository. I started by installing the charms from bzr to my local ubuntu 12.04 desktop running in a virtual machine. The new file structure is the following:

ubuntu@ubuntu-VirtualBox:~$ find charms/precise/drupal/
charms/precise/drupal/
charms/precise/drupal/hooks
charms/precise/drupal/hooks/db-relation-changed
charms/precise/drupal/hooks/install
charms/precise/drupal/hooks/start
charms/precise/drupal/hooks/stop
charms/precise/drupal/metadata.yml
charms/precise/drupal/README

When I install the mysql charm, which was downloaded from the remote charm repository, it works fine. However when I run the following command to deploy the new charm it fails with the following error message:

ubuntu@ubuntu-VirtualBox:~$ juju deploy --repository=charms local:precise/drupal
2012-05-09 10:01:05,671 INFO Searching for charm local:precise/drupal in local charm repository: /home/ubuntu/charms
2012-05-09 10:01:05,845 WARNING Charm '.mrconfig' has an error: CharmError() Error processing '/home/ubuntu/charms/precise/.mrconfig': unable to process /home/ubuntu/charms/precise/.mrconfig into a charm
Charm 'local:precise/drupal' not found in repository /home/ubuntu/charms
2012-05-09 10:01:06,217 ERROR Charm 'local:precise/drupal' not found in repository /home/ubuntu/charms

Is there some file missing in the drupal charm directory that juju needs to make the charm valid?

Also, I get the file processing error for the .mrconfig file also when deploying the mysql charm so is there something I need to change there perhaps?