Trying to clone a repository that is not in our routing table returns an error:

``` (fail)
$ rad clone rad:zVNuptPuk5XauitpCWSNVCXGGfXW --scope followed
✓ Tracking relationship established for rad:zVNuptPuk5XauitpCWSNVCXGGfXW with scope 'followed'
✗ Error: no seeds found for rad:zVNuptPuk5XauitpCWSNVCXGGfXW
```