Attempting to search Rucio when not logged in produces an unhelpful result

Specifically, the “scope” dropdown provides a single option:

Not logged in «django.contrib.sessions.backends.db.SessionStore object at 0x7f613a0b6860>, dict_keys(['_auth_user_id', '_auth_user_backend', '_auth_user_hash').

If login is required to search Rucio, we should say so.