backport: raise AuthenticationError if anon access is disabled on StartupView
requested to merge topic/default/raise-authenticationerror-if-anon-access-is-disabled-on-startupview into branch/default
If we want to access to a StartupView while we are not logged on an instance with anon access disabled, we need to set accessible_without_connection at True.
related: #595
Original commit by François Ferry