jsonify needs to return a string of {}, rather than a dict

lib/ansible/utils/__init__.py

@@ -122,7 +122,7 @@ def jsonify(result, format=False):
     ''' format JSON output (uncompressed or uncompressed) '''
 
     if result is None:
-        return {}
+        return "{}"
     result2 = result.copy()
     if format:
         return json.dumps(result2, sort_keys=True, indent=4)