django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named ‘MySQLdb’

今天执行数据库脚本生成python manage.py makemigrations，出现如下错误：django.core.exceptions.ImproperlyConfigured: Error loading MySQLdb module: No module named 'MySQLdb'。

import pymysql
pymysql.install_as_MySQLdb()