Trying to clone a repository that is not in our routing table returns an error:
$ rad clone rad:zVNuptPuk5XauitpCWSNVCXGGfXW
✓ Tracking relationship established for rad:zVNuptPuk5XauitpCWSNVCXGGfXW
✗ Clone failed: no seeds found for rad:zVNuptPuk5XauitpCWSNVCXGGfXW