This commit deals with Issue #3 on your repo

[osusoy]

Use Case:

• CAS login enabled
• CAS auto_create_users disabled
• login_required site setting enabled
• User logged into CAS as a user that is not in Redmine

The conditions above caused an eternal loop:

• CAS check detects valid TGT but login fails, redirecting the user
  to home page, which is protected so redirects to CAS check etc.

Implemented Fix:

• Created account/invalid_cas_user view with options to:
  • Login locally or
  • Logout and return to CAS server to login as valid user.
• Modified logout behavior to prevent CAS logout if the user chose
  the first option and logged in locally. In this case, the user is
  redirected to the invalid_cas_user view (inherant behavior)
• Added strings used in the fix to en locale file (and tidied up
  the ones that were already there.

NOTE:
I am using i18n v0.5.0 so vars in en.yml use its formatting. If
you're using an older version, you would need to replace
${some var} entries with {{some var}}

new file:   app/views/account/invalid_cas_user.rhtml
modified:   config/locales/en.yml
modified:   lib/redmine_cas.rb