Deletion of directories with snapshots will not output reason for trash move failure

When using trash-enabled FsShell to delete a directory that has snapshots, we se an error message saying "Failed to move to trash" but no explanation.

[hdfs@schu-enc2 ~]$ hdfs dfs -rm -r snap
2014-07-28 05:45:29,527 INFO  [main] fs.TrashPolicyDefault (TrashPolicyDefault.java:initialize(92)) - Namenode trash configuration: Deletion interval = 1440 minutes, Emptier interval = 0 minutes.
rm: Failed to move to trash: hdfs://schu-enc2.vpc.com:8020/user/hdfs/snap. Consider using -skipTrash option

If we use -skipTrash, then we'll get the explanation: "rm: The directory /user/hdfs/snap cannot be deleted since /user/hdfs/snap is snapshottable and already has snapshots"

It'd be an improvement to make it clear that dirs with snapshots cannot be deleted when we're using the trash.