Redmine

Hi!
I'm trying to develop a small plugin that sends an E-Mail to all users from a certain project. I guess, that there may be a plugin doing that already, but it is mainly for learning purposes.
I already know how to send emails to many users or a certain group. But somehow I don't manage to load a project. Everytime I do it I get a strange ActionDispatch::Cookies::CookieOverflow error... .
Here is how I try to do this:

Herve Harster = Project.find_by_identifier("example")

After this works, I think I will get the uses with the Project#users_by_role Method.
Can somebody tell me what is wrong with that code?