Do only follow HTTP and HTTPS redirects

We do not want to follow redirects to other protocols since they might allow an adversary to bypass network restrictions. (i.e. a redirect to ftp:// might be used to access files of a FTP server which might be in a secure zone and not be reachable from the net but from the ownCloud server)
Neither of the first two examples make sense to me. There doesn't seem to be much of a point in downloading stuff that is only meant to redirect. Hence my suggestion of treating these like errors and giving feedback to the user.