New utility function execute_query, wrapping cursor.execute.

This is a hack to avoid a problem with using %(foo)d in a query with a
NULL value.

cli/util.py

@@ -1,6 +1,12 @@
 import os
 import tempfile
 
+def execute_query(cursor, query, bindings):
+    for (key, val) in bindings.items():
+        if val == None:
+            query = query.replace('%(' + key + ')d', 'NULL')
+    cursor.execute(query, bindings)
+
 def make_result_dict(cursor, row):
     d = {}
     for i in xrange(len(row)):