cbrestore is not backwards compatible

Problem
When using cbrestore with a backup generated from a 4.5.1 the following exception is thrown:

Exception in thread w0: 

Traceback (most recent call last): 

File "/usr/lib64/python2.7/threading.py", line 811, in __bootstrap_inner 

self.run() 

File "/usr/lib64/python2.7/threading.py", line 764, in run 

self.__target(*self.__args, **self.__kwargs) 

File "/opt/couchbase/lib/python/pump.py", line 303, in run_worker 

src_conf_res = source.get_conflict_resolution_type() 

File "/opt/couchbase/lib/python/pump_bfd.py", line 430, in get_conflict_resolution_type 

json_file = open(files[0], "r") 

IndexError: list index out of range

Steps to Reproduce

1. Setup a 1 node cluster on 4.5.1 with the travel-sample bucket
2. Backup the cluster using {cbbackup}

   on 4.5.1.

   /opt/couchbase/bin/cbbackup http://localhost /vagrant/backup-test/couchbase_backup -u Administrator -p password

3. Setup a 1 node cluster on 4.6.2 with a empty name called test:
4. Restore the backup using the {cbrestore}

   on 4.6.2:

   /opt/couchbase/bin/cbrestore /vagrant/backup-test/couchbase_backup couchbase://10.112.162.101:8091 -B test -u Administrator -p password

Workaround
Use the cbrestore from Couchbase Server 4.5.1 to do the restore against the 4.6.2 cluster.

Expectation

1. For cbrestore to be backwards compatible
   1. If it is not possible to be backwards compatible a clear log message should be generated.