membase-cli requires python json module

A better error msg might help. How should end-user get the json (or other) modules.

[root@Config40VM0 1.6.0a]# ./bin/cli/membase --help
Traceback (most recent call last):
File "./bin/cli/membase", line 12, in ?
from listservers import *
File "/opt/NorthScale/1.6.0a/bin/cli/listservers.py", line 14, in ?
from restclient import *
File "/opt/NorthScale/1.6.0a/bin/cli/restclient.py", line 15, in ?
import json
ImportError: No module named json