pymysql.err.OperationalError: (2003, "Can't connect to MySQL server on 'mysql' ([Errno -2] Name or service not known)")
扩展应用调用栈：
1. /usr/lib/python2.7/site-packages/pymysql/connections.py, 第 619 行
raise exc
2. /usr/lib/python2.7/site-packages/pymysql/connections.py, 第 327 行
self.connect()
3. /usr/lib/python2.7/site-packages/pymysql/__init__.py, 第 94 行
return Connection(*args, **kwargs)
4. /usr/lib64/python2.7/site-packages/relstorage/adapters/drivers.py, 第 172 行
return self._connect(*args, **kwargs)
5. /usr/lib64/python2.7/site-packages/relstorage/adapters/mysql/drivers/__init__.py, 第 164 行
return super(AbstractMySQLDriver, self).connect(*args, **kwargs)
6. /usr/lib64/python2.7/site-packages/relstorage/adapters/mysql/drivers/pymysql.py, 第 87 行
return AbstractMySQLDriver.connect(self, *args, **kwargs)
7. /usr/lib64/python2.7/site-packages/relstorage/adapters/mysql/connmanager.py, 第 103 行
conn = self._db_connect(**params)
8. /usr/lib64/python2.7/site-packages/relstorage/adapters/mysql/connmanager.py, 第 133 行
replica_selector=self.ro_replica_selector)
9. /usr/lib64/python2.7/site-packages/relstorage/adapters/connmanager.py, 第 319 行
conn, cursor = self._do_open_for_load()
10. /usr/lib64/python2.7/site-packages/relstorage/adapters/connections.py, 第 158 行
new_conn, new_cursor = self._new_connection()
11. /usr/lib64/python2.7/site-packages/relstorage/adapters/connections.py, 第 244 行
self._open_connection()
12. /usr/lib64/python2.7/site-packages/relstorage/adapters/connections.py, 第 221 行
return self.call(callback, True, *args, **kw)
13. /usr/lib64/python2.7/site-packages/relstorage/storage/__init__.py, 第 738 行
self.__on_load_first_use
14. /usr/lib/python2.7/site-packages/ZODB/Connection.py, 第 737 行
invalidated = self._storage.poll_invalidations()
15. /usr/lib/python2.7/site-packages/ZODB/Connection.py, 第 921 行
self.newTransaction(None, False)
16. /usr/lib/python2.7/site-packages/ZODB/DB.py, 第 777 行
result.open(transaction_manager)
17. /usr/lib/python2.7/site-packages/zope/app/publication/zopepublication.py, 第 158 行
conn = self.db.open()
18. /usr/lib/python2.7/site-packages/zope/publisher/publish.py, 第 140 行
obj = publication.getApplication(request)
19. /usr/lib/python2.7/site-packages/zope/publisher/publish.py, 第 154 行
obj, request, exc_info, True)
20. /usr/lib/python2.7/site-packages/zope/app/wsgi/__init__.py, 第 65 行
request = publish(request, handle_errors=handle_errors)