Fix json output #441

twint/storage/write.py

@@ -65,6 +65,8 @@ def Csv(obj, config):
 
 def Json(obj, config):
     _obj_type = obj.__class__.__name__
+    if _obj_type == "str":
+        _obj_type = "username"
     null, data = struct(obj, config.Custom[_obj_type], _obj_type)
 
     base = addExt(config.Output, _obj_type, "json")