@Cris70: I think I know the cause now. The path http://yum.insynchq.com/fedora/21/media.1/media used to return an HTTP 403 which is used to specify that the access to the path is denied. If a path does not exist the code that should be returned is HTTP 404. I changed the settings of the S3 bucket to return a 404 instead. I still maintain though that for rpm-md repos zypper shouldn’t look for those paths.