Capistrano error with successfully copied files

Question

I'm using Capistrano to deploy an application that uses the theme_support plugin, and I added a method in my deployment recipe to automatically generate the theme cache during a deploy. When I deploy the application the theme files are copied/cached correctly, but Capistrano reports an error:

...
*** [err :: servername] cp -r /var/www/app/releases/20110218172542/themes/17/images /var/www/app/releases/20110218172542/public/themes/17/images
*** [err :: servername] cp -r /var/www/app/releases/20110218172542/themes/17/stylesheets /var/www/app/releases/20110218172542/public/themes/17/stylesheets
*** [err :: servername] cp -r /var/www/app/releases/20110218172542/themes/17/javascript /var/www/app/releases/20110218172542/public/themes/17/javascript
*** [err :: servername] cp -r /var/www/app/releases/20110218172542/themes/55/images /var/www/app/releases/20110218172542/public/themes/55/images
...

As far as I can tell, the copy command was successful, and running the rake task manually (or the copy commands manually) works without error. Any idea then why Capistrano is reporting those lines as err?

Edit: See the accepted answer below for the reason. I also filed bugs against Ruby and theme_support, so hopefully this will be resolved in the future.

Answer 1

Patrick Reagan says, "All those lines mean is that the output is being returned on STDERR (as opposed to STDOUT)" at http://groups.google.com/group/capistrano/browse_thread/thread/64e95a26af3035cd.

@jrdioko, I know you read his answer there, but I'm posting it here, too.