Trying to access an internal or private snippet while logged out leads to 404 and not login page

Internal discussion: https://dev.gitlab.org/gitlab/gitlabhq/issues/2533

Customer request:

Consider the next scenario:

• Log in in gitlab.com
• Create a snippet with "private" or "internal" visibility
• Log out from gitlab.com
• Try to access directly to the snippet: https://gitlab.com/snippets/6814
• One gets a 404 error

Isn't it suppose to redirect to the log-in page when trying to access a protected resource? The access to private/protected projects follows this workflow. GitLab redirects one to the login page and once authenticated, one arrives to the project or 404 if the project doesn't exists or not authorized to visit it. Shouldn't it be the same for snippets?

I think it makes sense since snippets are top-level resources like projects.