django2.2error:'str'object has no attribute decode

models 中有如下语句，执行python manage.py makemigrations:

    def __str__(self):
        return self.name

执行python manage.py makemigrations 报错如下:

 File "D:\pythonfile\venv\lib\site-packages\django\db\backends\mysql\operations.py", line 146, in last_executed_query
    query = query.decode(errors='replace')
AttributeError: 'str' object has no attribute 'decode'

修改如下，D:\pythonfile\venv\lib\site-packages\django\db\backends\mysql\operations.py:

    def last_executed_query(self, cursor, sql, params):
        # With MySQLdb, cursor objects have an (undocumented) "_executed"
        # attribute where the exact query sent to the database is saved.
        # See MySQLdb/cursors.py in the source distribution.
        query = getattr(cursor, '_executed', None)
        #if query is not None:   //注释此处
        #    query = query.decode(errors='replace') //注释此处
        return query