sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2006, "MySQL server has gone a
报错如下：
CR.CR_SERVER_GONE_ERROR, "MySQL server has gone away (%r)" % (e,) sqlalchemy.exc.OperationalError: (pymysql.err.OperationalError) (2006, "MySQL server has gone away解决办法：
app.config['SQLALCHEMY_POOL_RECYCLE'] = 200 （小于数据库连接）