query_cache: Clean up cjson remnants.

It was removed because it's actually rather buggy.

install-reddit.sh

@@ -132,7 +132,6 @@ python-bcrypt
 python-python-statsd
 python-snudown
 python-l2cs
-python-cjson
 python-lxml
 
 gettext

r2/r2/lib/db/tdb_cassandra.py

@@ -20,6 +20,7 @@
 # Inc. All Rights Reserved.
 ###############################################################################
 
+import json
 import inspect
 import pytz
 from datetime import datetime
@@ -56,8 +57,6 @@ debug = g.debug
 make_lock = g.make_lock
 db_create_tables = g.db_create_tables
 
-import json
-
 thing_types = {}
 
 TRANSIENT_EXCEPTIONS = (MaximumRetryException,)

r2/r2/models/query_cache.py

@@ -32,6 +32,7 @@ jobs.
 
 """
 
+import json
 import random
 import datetime
 import collections
@@ -45,7 +46,6 @@ from r2.lib.db import tdb_cassandra
 from r2.lib.db.operators import asc
 from r2.lib.db.sorts import epoch_seconds
 from r2.lib.utils import flatten, to36
-from r2.lib.db.tdb_cassandra import json
 
 
 CONNECTION_POOL = g.cassandra_pools['main']